[vtadmin] cell apis

[ajm188]

Description

vtadmin variants of:

• GetCellInfoNames (via /cells?names_only=true)
• GetCellInfo
• GetCellsAliases

Demo

➜  local git:(andrew/vtadmin/cell-apis) ✗ curl -s localhost:14200/api/cells\?cluster\=local | jq '.'
{
  "result": {
    "cell_infos": [
      {
        "cluster": {
          "id": "local",
          "name": "local"
        },
        "name": "zone1",
        "cell_info": {
          "server_address": "localhost:2379",
          "root": "/vitess/zone1"
        }
      }
    ]
  },
  "ok": true
}

Related Issue(s)

#8705

Checklist

• "Backport me!" label has been added if this change should be backported
• Tests were added or are not required -- TODO!
• Documentation was added or is not required

Deployment Notes

[github-actions]

Review Checklist

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Bug fixes

• There should be at least one unit or end-to-end test.
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Non-trivial changes

• There should be some code comments as to why things are implemented the way they are.

New/Existing features

• Should be documented, either by modifying the existing documentation or creating new documentation.
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Backward compatibility

• Protobuf changes should be wire-compatible.
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[doeg]

Thank you for doing this!!! Obligatory blocking question about tests but otherwise this is :chef-kiss: and I super appreciate it.

[doeg]

Obligatory question of "do we need tests for either of these"

[ajm188]

yes and yes

[ajm188]

annnd done

[doeg]

Just a question about """idiomatic go""": isn't this the same as if namesOnly && len(req.Cells) != 0?

[ajm188]

yuppppp (i originally had An Thought about doing the early return namesOnly loop in this section too, but never came back here), thanks!

[ajm188]

i'm gonna wait for #10233 and rebase, because i added a Dial call here that'll need to get cleaned up, if that's okay with you!