[16.0][FIX] fetch...folder: use message uid's not sequence

[NL66278]

When archiving messages, the messages get a new sequence through renumbering. To solve the problems this causes use the message uid's that are garanteed to remain constant for a message within a folder.

[NL66278]

@zamberjo Can you have a look at this?

[zamberjo]

Technically it seems correct, I have not been able to test it functionally.

[anmarmo1]

I am not clear about the initial problem that this change solves, but, the initial functionality is still correct, so for me the change is correct.

[ikus060]

As highlighted in PR #3222, the reverse processing of emails aims to address a similar issue to the one you're working on here.

But I fail to see the exact modification you are doing in this PR to retreive UID instead of sequences. It's probably lost in all the variable renames.

[NL66278]

@ikus060 I introduce the variable name message_uid instead of msgid, because it is a really different thing. msgid is basically the position of the message in the imap folder, and gets updated all the time because of insertions and deletions. message_uid however is constant (as long as the message remains in the same folder). However to work with the uid's the methods to work with messages are replaced by a single method on the connection, uid, with the original methodname as the first parameter:
connection.uid("search", charset, criteria)
connection.uid("fetch", message_uid, "(RFC822)")
...
Working with the message_uid's is intrinsically more reliable...

[ikus060]

ok, I see connection.uid("search", charset, criteria) vs connection.search(None, criteria)

I've missed that while looking at the changes. Thanks for pointing the changes.

[OCA-git-bot]

This PR has the approved label and has been created more than 5 days ago. It should therefore be ready to merge by a maintainer (or a PSC member if the concerned addon has no declared maintainer). 🤖

[NL66278]

/ocabot merge minor

[OCA-git-bot]

On my way to merge this fine PR!
Prepared branch 16.0-ocabot-merge-pr-3017-by-NL66278-bump-minor, awaiting test results.

[OCA-git-bot]

Congratulations, your PR was merged at 141d0a2. Thanks a lot for contributing to OCA. ❤️