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.

api/dto/dto.go

@@ -42,9 +42,17 @@ type ExecutionEnvironmentRequest struct {
 	ExposedPorts       []uint16 `json:"exposedPorts"`
 }
 
+// MappedPort contains the mapping from exposed port inside the container to the host address
+// outside the container.
+type MappedPort struct {
+	ExposedPort uint   `json:"exposedPort"`
+	HostAddress string `json:"hostAddress"`
+}
+
 // RunnerResponse is the expected response when providing a runner.
 type RunnerResponse struct {
-	ID string `json:"runnerId"`
+	ID          string        `json:"runnerId"`
+	MappedPorts []*MappedPort `json:"mappedPorts"`
 }
 
 // ExecutionResponse is the expected response when creating an execution for a runner.