Add persistent ids REST API

[malberts]

Closes #34 Replaces #36

Instead of hacking the core QueryInfo API, just add a simple REST API.

• Takes a list of page ids
• Returns an array of page_id => peristent_id.
• Non-existent page ids, or deleted page ids are not returned.
• Existing pages without persistent id get null
• Otherwise it gets the actual persistent id
• Does not include any batching or limits for now

Example: GET http://localhost:8484/rest.php/persistent-page-identifiers/v0/pages?ids=1|2|3|404

{
  "1": null,
  "2": "0193318b-43c6-701a-92b1-206b7f951c68"
}

(1 has no id, 2 has an id, 3 was deleted, 404 does not exist)

[JeroenDeDauw]

Some Claude suggestions:

• Use v1 instead of v0 for stable APIs
• Use commas instead of pipes for array parameters (more REST-like)

{
  "identifiers": {
    "1": null,
    "2": "0193318b-43c6-701a-92b1-206b7f951c68"
  },
  "meta": {
    "count": 3,
    "limit": 100
  }
}

I don't see much value in the meta part of the later suggestion, though wrapping the ID list in identifiers

[malberts]

v1

Done.

Use commas instead of pipes for array parameters (more REST-like)

Pipe is the MediaWiki way. Unfortunately, it's also hardcoded. Using it allows the API to understand the param is an array and it can validate the individual values as integers. Otherwise we need to change the param to a single string and then do the splitting and validation ourselves.

meta

That'll be more useful if there's batching involved. Otherwise the user can just do a count.

wrapping the ID list in identifiers

Done.