Enhancement: raise Error if param with the same variable is re-declared

[dukeraphaelng]

Currently it is possible to declare a param with the same variable more than once.

Example in a method-based framework

@[OpenAPI(
<<-YAML
  summary: get index
YAML
)]
def index
      limit1 = param(limit : Int32? = 100, description: "Page's limit")
      offset1 = param(offset : Int32? = 0, description: "Page's offset")
      limit2 = param(limit : Int32? = 100, description: "Items per page")
      offset2 = param(offset : Int32? = 0, description: "Page offset")

      render json: "index", type: String
end

This would render the following schema

  /api/portal/v1/instances:
    get:
      summary: get index
      parameters:
      - name: limit
        in: query
        description: Page's limit
        required: false
        schema:
          type: integer
      - name: offset
        in: query
        description: Page's offset
        required: false
        schema:
          type: integer
      - name: limit
        in: query
        description: Items per page
        required: false
        schema:
          type: integer
      - name: offset
        in: query
        description: Page offset
        required: false
        schema:
          type: integer
      responses:
        "200":
          description: OK
          content:
            text/yaml:
              schema:
                type: String

A compiler error should be raised if the param with the same variable is declared. more than once.