Cannot find symbol for a custom annotation on when using x-field-extra-annotation

Description

I want to add a field annotation to the generated field models via x-field-extra-annotation: '@CustomAnnotation'.
Now my annotation is custom and is in myproject com.project.annotation.CustomAnnotation

I tried to use schemaMappings:

<configuration>
  <schemaMappings>
    <schemaMapping>CustomAnnotation=com.bdl.ihubapi.annotation.CustomAnnotation</schemaMapping>
  </schemaMappings>
</configuration>

But I am having the following error after packagin:

cannot find symbol
[ERROR]   symbol:   class CustomAnnotation
[ERROR]   location: class com.project.model.Test

I also tried to include the following model.mustache:

{{>licenseInfo}}

package {{package}};

{{#imports}}import {{import}};
{{/imports}}
com.project.annotation.CustomAnnotation;

{{#models}}
{{#model}}
/**
 * {{classname}} : {{classVarName}}
 *
{{#description}} * {{{description}}}
 *
{{/description}}{{#vars}}
 * @param {{name}} {{description}}
{{/vars}} */
public class {{classname}} {{#parent}}extends {{{parent}}}{{/parent}} {{#serializableModel}}implements Serializable{{/serializableModel}} {
    {{#serializableModel}}
    private static final long serialVersionUID = 1L;
    {{/serializableModel}}
    {{#vars}}
    {{#isEnum}}
    /**
     * Gets or Sets {{{name}}}
     */
    @JsonAdapter({{{name}}}.EnumAdapter.class)
    public enum {{{name}}} {
        {{#allowableValues}}{{#enumVars}}{{{value}}}({{{value}}}){{^-last}},{{/-last}}{{/enumVars}}{{/allowableValues}}
        ;

        private String value;

        {{{name}}}(String value) {
            this.value = value;
        }

        public static {{{name}}} fromValue(String text) {
            for ({{{name}}} b : {{{name}}}.values()) {
                if (String.valueOf(b.value).equals(text)) {
                    return b;
                }
            }
            return null;
        }

        public String getValue() {
            return value;
        }

        @Override
        public String toString() {
            return String.valueOf(value);
        }

        public static class EnumAdapter extends TypeAdapter<{{{name}}}> {
            @Override
            public void write(final JsonWriter jsonWriter, final {{{name}}} enumeration) throws IOException {
                jsonWriter.value(enumeration.getValue());
            }

            @Override
            public {{{name}}} read(final JsonReader jsonReader) throws IOException {
                String value = jsonReader.nextString();
                return {{{name}}}.fromValue(String.valueOf(value));
            }
        }
    }
    {{/isEnum}}

    {{^isEnum}}
    {{>modelInnerClass}}
    {{/isEnum}}

    {{^isContainer}}
    private {{{datatypeWithEnum}}} {{name}};
    {{/isContainer}}

    {{#isContainer}}
    private {{{datatypeWithEnum}}} {{name}}{{#defaultValue}} = {{{.}}}{{/defaultValue}};
    {{/isContainer}}

    /**
     * Get {{{baseName}}}
     * @return {{{baseName}}}
     **/
    @ApiModelProperty({{#required}}required = true, {{/required}}{{^required}}required = false, {{/required}}{{#isReadOnly}}readOnly = true, {{/isReadOnly}}{{#isNullable}}nullable = true, {{/isNullable}}{{#minimum}}minimum = "{{{minimum}}}", {{/minimum}}{{#maximum}}maximum = "{{{maximum}}}", {{/maximum}}{{#minLength}}minLength = {{{minLength}}}, {{/minLength}}{{#maxLength}}maxLength = {{{maxLength}}}, {{/maxLength}}{{#pattern}}pattern = "{{{pattern}}}", {{/pattern}}{{#defaultValue}}"defaultValue" = "{{{defaultValue}}}",{{/defaultValue}}{{#allowableValues}}"allowableValues" = "{{{allowableValues.values}}}",{{/allowableValues}}"example" = "{{{example}}}","value" = "{{{description}}}"){{^required}}
    @JsonProperty("{{{baseName}}}"){{/required}}
    public {{{datatypeWithEnum}}} get{{{getter}}}() {
        return {{name}};
    }

    public void set{{{setter}}}({{{datatypeWithEnum}}} {{{name}}}) {
        this.{{name}} = {{{name}}};
    }
    {{/vars}}

}

{{/model}}
{{/models}}

and add it to the plugin configuration under the path myTemplates/spring/model.mustache:

<templateDirectory>${project.basedir}/myTemplates</templateDirectory>

openapi-generator version

v6.4.0

OpenAPI declaration file content or url

    Test:
      type: object
      properties:
        id:
          type: string
          format: uuid
          readOnly: true
          x-field-extra-annotation: '@CustomAnnotation'

Command line used for generation

mvn clean install

Steps to reproduce

Create a custom annotation interface and add it to the yaml filed x-field-extra-annotation: '@CustomAnnotation'.

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
public @interface CustomAnnotation {
    String id() default "";
}

Start with the Spring generator's model.mustache override and the Maven plugin schemaMappings configuration, then inspect the generated com.project.model.Test source for imports and the x-field-extra-annotation output. Reproduce with the supplied Test schema and CustomAnnotation, and confirm the generated model compiles when the annotation is available.