feat: change /metadata REST path to /v1/metadata

[spena]

Description

To be consistent with other Confluent platforms, the /metadata and /metadata/id paths were renamed to /v1/metadata and /v1/metadata/id.

Also, the /v1/metadata/id modified the output to this:

{
  "scope": {
    "path": [],
    "clusters": {
      "kafka-cluster": "ywqBIQ3PSU-K_5ttFkivCQ",
      "ksql-cluster": "default_"
    }
  },
  "id": ""
}

The kafka/ksql clusters ID are wrapped inside a clusters section. The path is also included, which for now is empty.

Testing done

• Updated unit tests
• Run manual tests

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")

[vcrfxia]

LGTM with one question:

The path is also included, which for now is empty.

What will it be in the future?

[big-andy-coates]

Thanks @spena

I'm left wondering what the path and id are for. Both are empty strings. Knowing little about this change, I would of thought that the id field of the meta request would return the id of either the Ksql cluster or this specific node.

[spena]

@big-andy-coates @vcrfxia I updated the PR to fix the assertion and add a couple of comments of what ID and PATH will be used in the future.

ID will be used to create a single URL string that includes the kafka & ksql cluster names which will be used by authorization services (as a CRN authority) to authorize access to this cluster. There's a plan to include this in 5.5 or later.

PATH is unsure what will be, but it seems it will contain the Cloud account organization where this cluster belongs to.

[spena]

I will merge this change as it is needed for 5.4 and has 1 approval (thanks @vcrfxia). I chat with @rodesai offline before he left for PTO, and he gave me his +1. Although not official, I leave this comment in case he denies it (but @rodesai was ok, :))