[REQ] [GO] Support yaml endpoints

Created by: mathnogueira

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

My API has two kinds of endpoints, most of them use application/json but a few rely on text/x-yaml. As it is today, we are forced to override the generated code in order to decode the request and encode the response properly for a YAML endpoint. It would be extremely helpful if the generator could generate code that supports encoding/decoding YAML.

Describe the solution you'd like

Be able to define an endpoint that accepts text/x-yaml and the go-server generator can generate an endpoint implementation capable of encoding/decoding YAML.

Describe alternatives you've considered

So far we could only achieve this by replacing the handler function for each YAML route, but this is not a good approach, it would be nice to have it out of the box.

Example of what we are doing:

routes[c.getRouteIndex("GetRunResultJUnit")].HandlerFunc = c.GetRunResultJUnit
routes[c.getRouteIndex("GetTestVersionDefinitionFile")].HandlerFunc = c.GetTestVersionDefinitionFile

Additional context

Example of endpoint:

/test.yaml:
    put:
      tags:
        - definition
      summary: Update a test using its definition 
      operationId: updateTestDefinition
      requestBody:
        content:
          text/x-yaml:
            schema:
              type: object
              properties:
                id:
                  type: string
                name:
                  type: string
                # rest of the properties
      responses:
        200:
          description: Test updated successfully