Horizon Server API: Specify content type as "application/json" and provide a response for all errors to enhance tooling support

[PatrickDittrich]

In order to enhance tooling support please specify the content type as application/json instead of */* and return a model for each response

I had success with adding a APIErrorResponseInfo model to the schamas and was then able to use Microsoft Kiota to generate an working rest client.

"components": {
  "schemas": {
    "....": {
    },
    "APIErrorResponseInfo": {
      "type": "object",
      "properties": {
        "errors": {
          "type": "array",
          "items": {
            "$ref": "#/components/schemas/APIError"
          },
          "description": "List of error objects containing error key and error message."
        },
        "status": {
          "type": "string",
          "description": "Response HTTP status code of the operation.",
          "example": "BAD_REQUEST"
        },
        "timestamp": {
          "type": "integer",
          "description": "Timestamp in milliseconds when the operation failed. Measured as epoch time.",
          "format": "int64",
          "example": 1763739153178
        }
      },
      "description": "Response for a failed API call."
    }
  }
}

And as example the modified refreshAccessToken definition

"/refresh": {
  "post": {
    "tags": [
      "Auth"
    ],
    "summary": "Refreshes access token from refresh token.",
    "operationId": "refreshAccessToken",
    "requestBody": {
      "content": {
        "application/json": {
          "schema": {
            "$ref": "#/components/schemas/RefreshToken"
          }
        }
      },
      "required": true
    },
    "responses": {
      "200": {
        "description": "OK",
        "content": {
          "application/json": {
            "schema": {
              "$ref": "#/components/schemas/AccessToken"
            }
          }
        }
      },
      "400": {
        "description": "Bad Request",
        "content": {
          "application/json": {
            "schema": {
              "$ref": "#/components/schemas/APIErrorResponseInfo"
            }
          }
        }
      },
      "429": {
        "description": "Too many requests",
        "content": {
          "application/json": {
            "schema": {
              "$ref": "#/components/schemas/APIErrorResponseInfo"
            }
          }
        }
      },
      "500": {
        "description": "Internal Server Error",
        "content": {
          "application/json": {
            "schema": {
              "$ref": "#/components/schemas/APIErrorResponseInfo"
            }
          }
        }
      }
    }
  }
}