[REQ] Aspnetcore Generator - add constructor to `model.mustache`

Is your feature request related to a problem? Please describe.

I want to instantiate a new object with private set attributes. I cannot easily instantiate a model object.

Describe the solution you'd like

In model.mustache add a constructor with all the attributes
Something like:

{{>partial_header}}
using System;
using System.Linq;
using System.Text;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Runtime.Serialization;
using Newtonsoft.Json;
{{#models}}
{{#model}}
{{#discriminator}}
using JsonSubTypes;
{{/discriminator}}
{{/model}}
{{/models}}
using {{packageName}}.Converters;

{{#models}}
{{#model}}
namespace {{modelPackage}}
{ {{#isEnum}}{{>enumClass}}{{/isEnum}}{{^isEnum}}

    /// <summary>
    /// {{description}}
    /// </summary>
    [DataContract]
    {{#discriminator}}
    [JsonConverter(typeof(JsonSubtypes), "{{{discriminatorName}}}")]
    {{#mappedModels}}
    [JsonSubtypes.KnownSubType(typeof({{{modelName}}}), "{{^vendorExtensions.x-discriminator-value}}{{{mappingName}}}{{/vendorExtensions.x-discriminator-value}}{{#vendorExtensions.x-discriminator-value}}{{{.}}}{{/vendorExtensions.x-discriminator-value}}")]
    {{/mappedModels}}
    {{/discriminator}}
    public {{#modelClassModifier}}{{modelClassModifier}} {{/modelClassModifier}}class {{classname}} : {{#parent}}{{{parent}}}, {{/parent}}IEquatable<{{classname}}>
    {        
    
#nullable enable

        /// <summary>
        /// Constructor
        /// </summary>
        public {{classname}}(
            {{#vars}}
             {{{dataType}}}{{^required}}?{{/required}} {{baseName}}{{^-last}},{{/-last}}
            {{/vars}}
        )
        { 
            {{#vars}}
            {{#isEnum}}
            {{#allowableValues}}
            {{#enumVars}}
                {{#isString}}
                
            if ({{baseName}}=="{{{value}}}")
            {
                {{baseName}} = "{{name}}";
            }
                {{/isString}}
            {{/enumVars}}
            {{/allowableValues}}
            {{name}} = ({{{datatypeWithEnum}}}{{^required}}?{{/required}}) Enum.Parse(typeof({{{datatypeWithEnum}}}{{#isNullable}}?{{/isNullable}}), {{baseName}});
            
            {{/isEnum}}
            {{^isEnum}}
            {{name}} = {{baseName}};
            {{/isEnum}}
            {{/vars}}
        }
        
        /// <summary>
        /// Empty constructor necessary for serialization
        /// </summary>
        public {{classname}}(){}

        {{#vars}}
        {{#items.isEnum}}
        {{#items}}
        {{^complexType}}
{{>enumClass}}
        {{/complexType}}
        {{/items}}
        {{/items.isEnum}}
        {{#isEnum}}
        {{^complexType}}
{{>enumClass}}
        {{/complexType}}
        {{/isEnum}}
        /// <summary>
        /// {{^description}}Gets or Sets {{{name}}}{{/description}}{{#description}}{{description}}{{/description}}
        /// </summary>{{#description}}
        /// <value>{{description}}</value>{{/description}}{{#required}}
        [Required]{{/required}}{{#pattern}}
        [RegularExpression("{{{pattern}}}")]{{/pattern}}{{#minLength}}{{#maxLength}}
        [StringLength({{maxLength}}, MinimumLength={{minLength}})]{{/maxLength}}{{/minLength}}{{#minLength}}{{^maxLength}}
        [MinLength({{minLength}})]{{/maxLength}}{{/minLength}}{{^minLength}}{{#maxLength}}
        [MaxLength({{maxLength}})]{{/maxLength}}{{/minLength}}{{#minimum}}{{#maximum}}
        [Range({{minimum}}, {{maximum}})]{{/maximum}}{{/minimum}}
        [DataMember(Name="{{baseName}}", EmitDefaultValue={{#isNullable}}true{{/isNullable}}{{^isNullable}}false{{/isNullable}})]
        {{#isEnum}}
        public {{{datatypeWithEnum}}}{{#isNullable}}?{{/isNullable}} {{name}} { get; set; }{{#defaultValue}} = {{{defaultValue}}};{{/defaultValue}}
        {{/isEnum}}
        {{^isEnum}}
        public {{{dataType}}}{{^required}}?{{/required}} {{name}} { get; {{#isReadOnly}}private {{/isReadOnly}}set; }{{#defaultValue}} = {{{defaultValue}}};{{/defaultValue}}
        {{/isEnum}}
        {{^-last}}

        {{/-last}}
        {{/vars}}
#nullable restore
        /// <summary>
        /// Returns the string presentation of the object
        /// </summary>
        /// <returns>String presentation of the object</returns>
        public override string ToString()
        {
            var sb = new StringBuilder();
            sb.Append("class {{classname}} {\n");
            {{#vars}}
            sb.Append("  {{name}}: ").Append({{name}}).Append("\n");
            {{/vars}}
            sb.Append("}\n");
            return sb.ToString();
        }

        /// <summary>
        /// Returns the JSON string presentation of the object
        /// </summary>
        /// <returns>JSON string presentation of the object</returns>
        public {{#parent}}{{^isMap}}{{^isArray}}new {{/isArray}}{{/isMap}}{{/parent}}string ToJson()
        {
            return Newtonsoft.Json.JsonConvert.SerializeObject(this, Newtonsoft.Json.Formatting.Indented, new Newtonsoft.Json.JsonSerializerSettings
            {
                NullValueHandling = NullValueHandling.Ignore
            });
        }

        /// <summary>
        /// Returns true if objects are equal
        /// </summary>
        /// <param name="obj">Object to be compared</param>
        /// <returns>Boolean</returns>
        public override bool Equals(object obj)
        {
            if (obj is null) return false;
            if (ReferenceEquals(this, obj)) return true;
            return obj.GetType() == GetType() && Equals(({{classname}})obj);
        }

        /// <summary>
        /// Returns true if {{classname}} instances are equal
        /// </summary>
        /// <param name="other">Instance of {{classname}} to be compared</param>
        /// <returns>Boolean</returns>
        public bool Equals({{classname}} other)
        {
            if (other is null) return false;
            if (ReferenceEquals(this, other)) return true;
            return {{#vars}}{{^isContainer}}
                (
                    {{name}} == other.{{name}} ||
                    {{^vendorExtensions.x-is-value-type}}{{name}} != null &&{{/vendorExtensions.x-is-value-type}}
                    {{name}}.Equals(other.{{name}})
                ){{^-last}} && {{/-last}}{{/isContainer}}{{#isContainer}}
                (
                    {{name}} == other.{{name}} ||
                    {{^vendorExtensions.x-is-value-type}}{{name}} != null &&
                    other.{{name}} != null &&
                    {{/vendorExtensions.x-is-value-type}}{{name}}.SequenceEqual(other.{{name}})
                ){{^-last}} && {{/-last}}{{/isContainer}}{{/vars}}{{^vars}}false{{/vars}};
        }

        /// <summary>
        /// Gets the hash code
        /// </summary>
        /// <returns>Hash code</returns>
        public override int GetHashCode()
        {
            unchecked // Overflow is fine, just wrap
            {
                var hashCode = 41;
                // Suitable nullity checks etc, of course :)
                {{#vars}}
                    {{^vendorExtensions.x-is-value-type}}if ({{name}} != null){{/vendorExtensions.x-is-value-type}}
                    hashCode = hashCode * 59 + {{name}}.GetHashCode();
                {{/vars}}
                return hashCode;
            }
        }

        #region Operators
        #pragma warning disable 1591

        public static bool operator ==({{classname}} left, {{classname}} right)
        {
            return Equals(left, right);
        }

        public static bool operator !=({{classname}} left, {{classname}} right)
        {
            return !Equals(left, right);
        }

        #pragma warning restore 1591
        #endregion Operators
    }
{{/isEnum}}
{{/model}}
{{/models}}
}

Start by locating the ASP.NET Core generator's model.mustache template and read how model variables, enums, and read-only properties are rendered. Add the requested all-attribute constructor while preserving the existing empty serialization constructor; done means generated C# models can be instantiated with their attributes.