Unarchive thread to delete messages

[ckcr4lyf]

Currently, if a thread is archived, we just skip those messages. Instead, we can try and unarchive the thread, then delete messages (this is what discord does if you right-click & delete a message in an archived thread - first unarchive, then delete).

Since the while loop already attempts twice, if we fail due to archived, we can:

1. Attempt to unarchive
2. If unarchive successfully, return RETRY , so caller fn will try and delete again
3. If fail to unarchive, skip (existing logic).

This can help people delete more messages.

Additionally, while implementing this I found a bug in system messages - Thread started messages (type 21) are not deletable (as per Discord, see: https://discord.com/developers/docs/resources/channel#message-object-message-types)

Updated the filter logic to be <=20 so 21 is not counted.

[ckcr4lyf]

Before: Skip archived threads

After (v0): Unarchive (but fail on system message type 21)

After (v1): Unarchive, skip system message

[ckcr4lyf]

Actually, @victornpb , not sure if you are OK with this behavior (i.e auto-unarchive). Bug #516 seems to suggest a user would not expect this behavior, so maybe we need to either explicitly document it or offer it as an option?

(Personally: If I want to wipe my messages from a channel, I would want to wipe from threads under it as well.)

[RainerZufall187]

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