Initial POC for a facility that uses redirects

[Fingel]

This is how this flow works:

User is at the TOM:

1. The facility class constructs a URL that points to the OCS. This URL contains query parameters that correspond to the chosen Target's attributes.
2. The facility class also constructs a callback url, which points to the internal tom_observations:callback view. This callback url contains query parameters for the facility class name, the target id, but leaves the observation id blank (this is to be provided by the observation portal)
3. The facility class simply presents a the combined link to the OCS (with the callback url appended as a query parameter). User clicks on the link to the OCS.

Now at the OCS:

1. The OCS presents the observation create form, and pre-fills in the target fields based on the query params.
2. The user submits the observation.
3. Instead of doing whatever the OCS does, it redirects to the callback url created in the previous step 2 with the newly created observation_id appended.

Now back at the TOM:

1. The callback url creates an ObservationRecord object from the query parameters passed in from the OCS: target_id, facility, and observation_id.
2. The user is sent to the ObservationRecord detail view of the newly created observation record. There is no distinction between records created using the built in OCS form or those created via the redirect flow.

[jchate6]

@Fingel is there a branch of the OCS that this relies on to work?

The redirection to the OCS looks good, but I'm guessing this relies on OCS changes to be fully functional. It would be nice to have something running locally before merging this.

[Fingel]

OCS PR here: LCOGT/observation-portal-frontend#130

[jchate6]

Screencast-2025-12-03-13_02.mp4