[REQ][spring] Feature x-implements is not supported

[jorgerod]

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

x-implements extension is not supported for spring server (for the different java clients it is supported).

OpenAPI declaration file content or url

openapi: 3.0.0
components:
  schemas:
    MyDtoImpl:
      type: object
      description: To be override with the schema id
      x-implements: ['org.data.MyDto']
      properties:
        data:
          description: Data compliant with the schema defined at the description field
          type: object

x-implements is not taken into account

Expected generation

public class MyDtoImpl implements org.data.MyDto  {
...
}

Describe the solution you'd like

Adapt the pojo.mustache template to take this extension into account.

openapi-generator/modules/openapi-generator/src/main/resources/JavaSpring/pojo.mustache

Lines 24 to 26 in b979ecc

	{{>generatedAnnotation}}
	public class {{classname}} {{#parent}}extends {{{.}}}{{/parent}}{{^parent}}{{#hateoas}}extends RepresentationModel<{{classname}}> {{/hateoas}}{{/parent}} {{#serializableModel}}implements Serializable{{/serializableModel}} {
	{{#serializableModel}}

What do you thinki?

[wing328]

Closed via #11784 by @borsch (Thank you)

@jorgerod please pull the latest master to give it another try.