Return mapped ports when requesting runners

We now store the mapped ports returned by Nomad locally in our runner
struct and return them when requesting the runner. The returned ip
address is in most Nomad setups not reachable from external users.

docs/swagger.yaml

@@ -144,6 +144,21 @@ paths:
                     description: The UUID of the provided runner
                     type: string
                     example: 123e4567-e89b-12d3-a456-426614174000
+                  mappedPorts:
+                    description: Array containing the addresses of the mapped ports specified in the execution environment.
+                    type: array
+                    items:
+                      description: The exposedPort inside the container is reachable on the returned hostAddress.
+                      type: object
+                      properties:
+                        exposedPort:
+                          description: The port inside the container.
+                          type: uint
+                          example: 80
+                        hostAddress:
+                          description: The address which can be contacted to reach the mapped port.
+                          type: string
+                          example: 10.224.6.18:23832
         "400":
           $ref: "#/components/responses/BadRequest"
         "401":