[feature] Conversations API (#3013)

* Implement conversations API

* Sort and page conversations by last status ID

* Appease linter

* Fix deleting conversations and statuses

* Refactor to make migrations automatic

* Lint

* Update tests post-merge

* Fixes from live-fire testing

* Linter caught a format problem

* Refactor tests, fix cache

* Negative test for non-DMs

* Run conversations advanced migration on testrig startup as well as regular server startup

* Document (lack of) side effects of API method for deleting a conversation

* Make not-found check less nested for readability

* Rename PutConversation to UpsertConversation

* Use util.Ptr instead of IIFE

* Reduce cache used by conversations

* Remove unnecessary TableExpr/ColumnExpr

* Use struct tags for both unique constraints on Conversation

* Make it clear how paging with GetDirectStatusIDsBatch should be used

* Let conversation paging skip conversations it can't render

* Use Bun NewDropTable

* Convert delete raw query to Bun

* Convert update raw query to Bun

* Convert latestConversationStatusesTempTable raw query partially to Bun

* Convert conversationStatusesTempTable raw query partially to Bun

* Rename field used to store result of MaxDirectStatusID

* Move advanced migrations to their own tiny processor

* Catch up util function name with main

* Remove json.… wrappers

* Remove redundant check

* Combine error checks

* Replace map with slice of structs

* Address processor/type converter comments

- Add context info for errors
- Extract some common processor code into shared methods
- Move conversation eligibility check ahead of populating conversation

* Add error context when dropping temp tables

internal/processing/account/delete.go

@@ -460,6 +460,14 @@ func (p *Processor) deleteAccountPeripheral(ctx context.Context, account *gtsmod
 
 	// TODO: add status mutes here when they're implemented.
 
+	// Delete all conversations owned by given account.
+	// Conversations in which it has only participated will be retained;
+	// they can always be deleted by their owners.
+	if err := p.state.DB.DeleteConversationsByOwnerAccountID(ctx, account.ID); // nocollapse
+	err != nil && !errors.Is(err, db.ErrNoEntries) {
+		return gtserror.Newf("error deleting conversations owned by account: %w", err)
+	}
+
 	// Delete all poll votes owned by given account.
 	if err := p.state.DB.DeletePollVotesByAccountID(ctx, account.ID); // nocollapse
 	err != nil && !errors.Is(err, db.ErrNoEntries) {