Support for address books larger than 1000 contacts

[andxblink]

Description

The contacts view shows a maximum of 1000 contacts. My Stalwart instance
has 5,413 contacts in a single address book, but Bulwark only displays
the first 1000.

Root Cause

The browser-side JMAP call uses a hardcoded limit: 1000 in
ContactCard/query and does not paginate to fetch additional results:

{
  "using": ["urn:ietf:params:jmap:core",
"urn:ietf:params:jmap:contacts"],
  "methodCalls": [
    ["ContactCard/query", {"accountId": "g", "limit": 1000}, "0"],
    ["ContactCard/get", {"accountId": "g", "#ids": {"resultOf": "0",
"name": "ContactCard/query", "path": "/ids"}}, "1"]
  ]
}

When the query returns 1000 IDs, the subsequent ContactCard/get fetches
those 1000 and stops. No further pages are requested.

Additional Note

The default Stalwart maxObjectsInGet is 500, so out of the box this also
causes a requestTooLarge error on the ContactCard/get call (1000 IDs >
500 limit), resulting in 0 contacts displayed. I had to raise
jmap.protocol.get.max-objects to 5000 on Stalwart to get any contacts to
show at all.

Expected Behavior

• Paginate ContactCard/query using position / anchor to fetch all
  contacts
• Batch ContactCard/get calls to stay within maxObjectsInGet (respect
  the server's advertised limit from the JMAP session capabilities)

Environment

• Bulwark Webmail v1.4.4
• Stalwart Mail Server v0.15.5
• 5,413 contacts in one address book

[rathlinus]

Will be in next version 1.4.5: github.com/bulwarkmail/webmail/commit/6cff98ddb82366332564d96e12e2650b722f408c