[C# DOTNET] Incorrect example JSON generated for aspnetcore server stub

Description

The generated exampleJson for response body is incorrectly escaped if an "example" tag is provided on the property level, when using the .NET Core 3.0 generated code for server stubs.

The API spec:

      responses:
        '200':
          description: >
            All good
          content:
            application/json:
              schema:
                type: object
                
                properties:
                  pv-installation:
                    type: string
                  links:
                    type: object
                    example: 
                      economics: 
                        href: >-
                          /pvInstallation/economics?roof-size=100&irradiation=1234&tilt=45&azimuth=274
                    properties:
                      economics:
                        $ref: '#/components/schemas/Link'

will produce an exampleJson with incorrect escaped quotes in the controller (DefaultAPI.cs) which does not deserialize :

exampleJson = "{\n  \"links\" : \"{\\"economics\\":{\\"href\\":\\"/pvInstallation/economics?roof-size=100&irradiation=1234&tilt=45&azimuth=274\\"}}\",\n  \"pv-installation\" : \"pv-installation\"\n}";

By contrast, it works nicely if the example is provided for all properties on schema level, such as:

      responses:
        '200':
          description: >
            All good
          content:
            application/json:
              schema:
                type: object
                example: 
                  pv-installation: Tjoho
                  economics: 
                    href: >-
                      /pvInstallation/economics?roof-size=100&irradiation=1234&tilt=45&azimuth=274
            
                properties:
                  pv-installation:
                    type: string
                  links:
                    type: object

                    properties:
                      economics:
                        $ref: '#/components/schemas/Link'

or for each property in the property definition.
Both these options will produce a correct exampleJson of:

exampleJson = "{\n  \"pv-installation\" : \"Tjoho\",\n  \"economics\" : {\n    \"href\" : \"/pvInstallation/economics?roof-size=100&irradiation=1234&tilt=45&azimuth=274\"\n  }\n}";

Swagger-codegen version

3.0.21 via swaggerhub

Swagger declaration file content or url

Open API 3.0 specification for reproduction: https://gist.github.com/AndersAko/76c97f7baca0693fbb8298a1d8e3206d

Command line used for generation

Steps to reproduce

Related issues/PRs

Suggest a fix/enhancement

Use the linked OpenAPI 3.0 reproduction and inspect the generated DefaultAPI.cs for the response body's exampleJson. Compare output from a property-level example with the working schema-level examples, then verify that the generated JSON no longer contains incorrectly escaped nested quotes and can be deserialized.