Add endpoint to collect location action timepoints

As a frontend developer I want to have one endpoint to extract all the timepoints for that there is a location action (either begin or end) no matter if it is for a dynamic location or a static one.

Possible paylaod:

GET /controller/configurations/<int:configuration_id>/location-action-timepoints

[{
  "timepoint": "2022-01-01T00:00:00Z",
  "type": "configuration_static_location",
  "attributes": {
      "begin_description": "bla bla",
       // ...
   },
}, {
 "timepoint": "2022-01-05T00:00:00Z",
  "type": "configuration_dynamic_location",
  "attributes": {
      "begin_description": "bla bla",
       // ...
   },
}]

Please note: I think the types must be adjusted further to represent that there are begin dates & end dates.

Acceptance criteria:

• endpoint is available under /controller/configurations/<int:configuration_id>/location-action-timepoints
• it contains all begin dates of static location actions
• it contains all begin dates of dynamic location actions
• it just gets the configuration id via the url parameter
• result array is sorted by timestamp (oldest first)
• the payload should contain both begin & end dates (if available)
• Test coverage