Core-API activities implementation

[zehnm]

This is a tracking issue for the API implementation in the simulator. The implemented operations will be marked completed, when a new core-simulator version is released.

core-simulator release 0.10.0:

• [x] HEAD /activities
• [x] GET /activities
• [x] POST /activities
  • clone from macro or remote entity is not yet implemented, but this is not required for the web-configurator.
• [x] DELETE /activities
• GET /activities/{entityId}
  • entity commands are not yet included (or not returned as specified in OpenAPI v0.10.2)
• PATCH /activities/{entityId}
  • partially implemented
• [x] DELETE /activities/{entityId}

core-simulator release 0.10.2:

• [x] GET /activities/{entityId}

core-simulator release 0.10.3:

• [x] PATCH /activities/{entityId}

[zehnm]

Closing issue: all endpoints are implemented and can be used for the web-configurator. Additional validation checks will be added in future updates.