remove(api): Versions 1 to 2 are Gone or Not Found

[Flix6x]

Remove API versions 1.0, 1.1, 1.2, 1.3 and 2.0, while allowing hosts to switch between HTTP status 410 (Gone) and HTTP status 404 (Not Found) responses.

Follow-up issue: remove old data classes.

[nhoening]

For how long do you plan to allow users to return 410 for these routes - one more version?

[Flix6x]

For how long do you plan to allow users to return 410 for these routes - one more version?

Yes, one more. So we'd have this sequence:

1. 200 with toggle to 410 (blackout test) and relevant headers
2. 410 with toggle to 200 (sunset rollback)
3. 404 with toggle to 410 (removal rollback)
4. 404 (routes removed)

I could ask in the TSC whether stage 3 is redundant.

[nhoening]

I think this way to explain our policy would be great on https://flexmeasures.readthedocs.io/en/latest/api/introduction.html#deprecation-and-sunset

[nhoening]

I approve, if the discussed addition ti the docs happens: document the steps of an deprecation/sunset/gone cycle

[Flix6x]

@nhoening Maybe do a quick check on my documentation changes?

[nhoening]

I like it, thanks!

• In my opinion, stage 3 is maybe not needed and overcomplicates things a bit. Not sure when and how we should make this decision. We can ask in the TAC. Surely before 0.14.
• Do we already implement support for these stages in the flexmeasures_client?

[Flix6x]

• I agree to elevate the discussion. In the LF Energy TAC, or FlexMeasures TSC? I was thinking the latter.
• The client will check for relevant headers and log warnings, and will raise exceptions for 4xx status codes.

[nhoening]

Yes, TSC