feat(common): improve problem schema (#41)

Author: matoous

common.yaml

@@ -14,19 +14,19 @@ components:
           type: string
           format: uri
           description: A URI reference that identifies the problem type.
+          example: https://developer.sumup.com/problem/not-found
         title:
           type: string
           description: A short, human-readable summary of the problem type.
+          example: Requested resource couldn't be found.
         status:
           type: integer
           description: The HTTP status code generated by the origin server for this occurrence of the problem.
-          minimum: 400
-          maximum: 600
-          exclusiveMaximum: true
-          example: 400
+          example: 404
         detail:
           type: string
           description: A human-readable explanation specific to this occurrence of the problem.
+          example: The requested resource doesn't exist or does not belong to you.
         instance:
           type: string
           format: uri