CDRIVER-3969 error when creating uncompleted cursor with no server ID

[kevinAlbs]

Patch build: https://spruce.mongodb.com/version/6495b91ed1fe075c5a548f5a

Summary

Return an error if mongoc_cursor_new_from_command_reply(_with_opts) is called with a non-zero cursor ID and no server ID.

Background & Motivation

mongoc_cursor_new_from_command_reply_with_opts is expected to be used by drivers wrapping the C driver to create a mongoc_cursor_t from a server reply.

The server reply indicates whether a cursor is completed by a non-zero cursor.id field. Example with mongosh:

> db.coll.drop()
true
> db.coll.insertMany([{_id:0},{_id:1}])
{ acknowledged: true, insertedIds: { '0': 0, '1': 1 } }
> db.runCommand({find: "coll", batchSize: 1})
{
  cursor: {
    firstBatch: [ { _id: 0 } ],
    id: Long("2413824932427886184"),
    ns: 'test.coll'
  },
  ok: 1,
  '$clusterTime': {
    clusterTime: Timestamp({ t: 1687535574, i: 3 }),
    signature: {
      hash: Binary(Buffer.from("0000000000000000000000000000000000000000", "hex"), 0),
      keyId: Long("0")
    }
  },
  operationTime: Timestamp({ t: 1687535574, i: 3 })
}

The cursor is iterated by sending a getMore with the cursor ID:

> db.runCommand({getMore: Long("2413824932427886184"), batchSize: 1, collection: "coll"})
{
  cursor: {
    nextBatch: [ { _id: 1 } ],
    id: Long("2413824932427886184"),
    ns: 'test.coll'
  },
  ok: 1,
  '$clusterTime': {
    clusterTime: Timestamp({ t: 1687535645, i: 1 }),
    signature: {
      hash: Binary(Buffer.from("0000000000000000000000000000000000000000", "hex"), 0),
      keyId: Long("0")
    }
  },
  operationTime: Timestamp({ t: 1687535645, i: 1 })
}

And the server indicates the cursor is closed with a 0 cursor.id:

> db.runCommand({getMore: Long("2413824932427886184"), batchSize: 1, collection: "coll"})
{
  cursor: { nextBatch: [], id: Long("0"), ns: 'test.coll' },
  ok: 1,
  '$clusterTime': {
    clusterTime: Timestamp({ t: 1687535655, i: 1 }),
    signature: {
      hash: Binary(Buffer.from("0000000000000000000000000000000000000000", "hex"), 0),
      keyId: Long("0")
    }
  },
  operationTime: Timestamp({ t: 1687535655, i: 1 })
}

An uncompleted cursor can be iterated by sending a "getMore" command or closed with a "killCursors" command. The command is expected to be sent to the same server the cursor was created.

This PR proposes returning an error if mongoc_cursor_new_from_command_reply(_with_opts) is called with a non-zero cursor ID and a zero server ID.

If creating an uncompleted cursor with a zero server ID, the cursor does not know the server that created the cursor. The cursor cannot guarantee the "getMore" or "killCursors" commands will be sent to the originating server. If the commands are sent to the wrong server, this results in a "cursor not found" error for "getMore" or the originating server resources not being destroyed by "killCursors".

[joshbsiegel]

LGTM besides minor comment

[joshbsiegel]

Logic could be simplified here being that there's no other work being done inside of this if statement. However, if you'd rather leave the if statements separate for readability and comments then that's fine as well.

Suggested change

	if (0 != cursor->cursor_id) {
	if (0 != cursor->cursor_id && 0 == cursor->server_id) {

[kevinAlbs]

Seems like a reasonable simplification. Removed the nested if.