*: remove v1/alerts/groups API endpoint

[simonpasquier]

Closes #1508

I had this change for a while in my backlog, just rebased on master to fix some conflicts.

[mxinden]

Looks good to me. Thanks for the thorough cleanup. Just to ensure, that we are mentioning this in the release notes, would you please add an entry to the Next release section of CHANGELOG.md in this PR?

[mxinden]

Great! Thanks for moving APIAlert into api/api.go.

[simonpasquier]

@mxinden done!

[stuartnelson3]

alertSlice() on dispatch.go#246 can also be removed, then this is good to go

[mxinden]

In case one of you clicks merge first, would you mind squashing? Makes preparing the CHANGELOG.md easier for the next release.

[stuartnelson3]

squash4lyfe

[mxinden]

@simonpasquier would you mind resolving the conflict?

[simonpasquier]

@mxinden done

[mxinden]

Thanks @simonpasquier!

[mpursley]

Hi @simonpasquier @mxinden, sounds like removing the "v1/alerts/groups" endpoint from the V1 API has broken compatibility with some external clients.. e.g.
"Don't work with the latest version api (v2) alertmanager" - prymitive/karma#115
"Incompatibility with alertmanager 0.16.x" - cloudflare/unsee#273

I wonder if it make sense to just put api/v1/alerts/groups back in? (E.g. just re-add the code that was removed from this PR?)

As:

1. This is the only endpoint from the V1 API that was removed, and
2. It sounds like this endpoint was just removed for reasons like "this is a size-able chunk of code that probably hasn't been used for over a year". Though, there are some remote clients (like Unsee and Karma) that are using this endpoint, so it might be worth putting it back into the V1 API, to continue to support these API clients?

[roidelapluie]

Yes +1 for adding it back. We use karma.

[simonpasquier]

@mpursley sorry for the pain, if I would have known that that endpoint was used, it wouldn't have been removed probably. The v1 API is deprecated and the plan is to implement something similar with the v2 API to accommodate karma (see #868).

[mpursley]

@mpursley sorry for the pain, if I would have known that that endpoint was used, it wouldn't have been removed probably. The v1 API is deprecated and the plan is to implement something similar with the v2 API to accommodate karma (see #868).

Yes, understood. It looks like #868 is now updated to "P2", so hopefully that update/fix gets added soon(ish). Just keep in mind that there will be users out there that are not able to update unsee/karma or alertmanager until this endpoint gets returned or replaced.

Thx @simonpasquier