Route53: keep MX priority and SRV weight/port when updating or deleting records - #2224

Route53: keep MX priority and SRV weight/port when updating or deleting records

Description

_to_record splits the MX priority and the SRV priority, weight and port out of the value Route53 stores, but they are not all put back when a record is written:

• update_record on a record that is part of a multi value set (e.g. one of the MX values) sends every value without its priority, so the DELETE doesn't match what Route53 stores and the CREATE values are invalid.
• update_record and delete_record on SRV records send priority target instead of priority weight port target. With the list_records fixture, deleting the SRV record sends 1 xmpp-server.example.com. instead of 1 10 5269 xmpp-server.example.com..

#2177 fixed this for multi value MX deletes. This uses its _to_record_value helper in the update path and in _post_changeset as well, and makes it restore the SRV weight and port.

Three new tests check the posted changeset (multi value MX update, multi value SRV delete, single value SRV update), plus an SRV case in test_to_record_value; they fail on trunk and pass with the fix. libcloud/test/dns passes (541 tests), and black, isort, flake8 and pylint -E pass. I couldn't run it against real Route53.

Status

done, ready for review

Checklist (tick everything that applies)

• Code linting (required, can be done after the PR checks)
• Documentation
• Tests
• ICLA (required for bigger changes)