[CSHARP] int64 being converted to long correctly but given a float default so won't compile

Description

As per title, I am trying to generate the model classes for the docker api swagger spec, this contains a number of nullable properties of format "integer" and format "int64". They are being generated as long? but then given a default value which indicates it is a float, e.g. long? size = -1F which causes a compiler error.

Swagger-codegen version

3.0.65

Swagger declaration file content or url

      UsageData:
        type: "object"
        x-nullable: true
        x-go-name: "UsageData"
        required: [Size]
        description: |
          Usage details about the volume. This information is used by the
          `GET /system/df` endpoint, and omitted in other endpoints.
        properties:
          Size:
            type: "integer"
            format: "int64"
            default: -1
            description: |
              Amount of disk space used by the volume (in bytes). This information
              is only available for volumes created with the `"local"` volume
              driver. For volumes created with other volume drivers, this field
              is set to `-1` ("not available")
            x-nullable: false

produces

        /// <summary>
        /// Initializes a new instance of the <see cref="VolumeUsageData" /> class.
        /// </summary>
        /// <param name="size">Amount of disk space used by the volume (in bytes). This information is only available for volumes created with the &#x60;\&quot;local\&quot;&#x60; volume driver. For volumes created with other volume drivers, this field is set to &#x60;-1&#x60; (\&quot;not available\&quot;)  (required) (default to -1F).</param>
       
        public VolumeUsageData(long? size = -1F)

Command line used for generation

docker run --rm --network=host -v ${PWD}:/local swaggerapi/swagger-codegen-cli-v3 generate \
-i http://localhost:3000/swagger.yaml \
-l csharp \
-Dmodels \
--additional-properties=resolveMethodConflicts=true \
-c /local/config.json \
-o /local/out/csharp

Steps to reproduce

1. Using the following docker swagger spec (which originally came from here)
   swagger.yaml.zip

2. Host the swagger-ui mounting this spec file in

docker run -p 3000:8080 -e SWAGGER_JSON=/swagger.yaml -v $(pwd)/swagger.yaml:/swagger.yaml swaggerapi/swagger-ui

3. Generate the C# code with the following

docker run --rm --network=host -v ${PWD}:/local swaggerapi/swagger-codegen-cli-v3 generate \
-i http://localhost:3000/swagger.yaml \
-l csharp \
-Dmodels \
--additional-properties=resolveMethodConflicts=true \
-c /local/config.json \
-o /local/out/csharp

4. Observe all the default float values being given for longs when you try to build it.

Related issues/PRs

None found

Suggest a fix/enhancement

Feels like somewhere along the way nullable int64 types are being treated as floats somewhere between the correct mapping into an actual C# type (a long?) and working out what default value to use.

Reproduce the issue with the Docker-based csharp generation command and the supplied Swagger specification. Trace how nullable int64 properties are mapped to long? and how their default values are rendered in the generated constructor; done means the generated C# uses a valid long default and builds without compiler errors.