feat: move messages to junk folder

[kesselb]

For #4101

To Do

• Decide: Merge JunkSettings into AccountDefaultSettings
• Decide: Rename "Mark as Spam" to "Move to Spam" with checkbox "Move message to Junk" enabled
• Inline documentation about the action/getter behavior
• Testing

Test cases

Message List	Message View

1. Add a new account. See a different icon for an existing folder/mailbox with the special role "junk".
2. Open account settings. A section "Junk settings" exist. The checkbox "Move message to Junk" is off by default.
3. Open action menu from the message list. Click "Mark as Spam". The message is flagged as spam, but not moved.
4. Open action menu from the message view. Click "Mark as Spam". The message is flagged as spam, but not moved.
5. Open account settings. Toggle checkbox "Move message to Junk".
6. Open action menu from the message list. Click "Mark as Spam". The message is flagged as spam and moved.
7. Open action menu from the message view. Click "Mark as Spam". The message is flagged as spam and moved.
8. Open junk mailbox and repeat 6 and 7.

[ChristophWurst]

can we assume the name to be always exactly like that? what about capitalization? personal namspace?

[jancborchardt]

Decide: Rename "Mark as Spam" to "Move to Spam" with checkbox "Move message to Junk" enabled

It should stay a simple "Mark as spam" action. It is expected from (the majority of) other clients that "Mark as spam" will also move it to spam/junk.

[kesselb]

I will add the junk mailbox to the default folders and use a different section for the move junk toggle.
It looks similar to Richard's trash retention feature then.

[ChristophWurst]

Works

[ChristophWurst]

OCA\Mail\Tests\Integration\Db\MailAccountTest::testMailAccountConstruct
Failed asserting that two arrays are equal.
--- Expected
+++ Actual
@@ @@
     'quotaPercentage' => null
     'trashRetentionDays' => 60
     'name' => 'Peter Parker'
+    'junkMailboxId' => null
+    'moveJunk' => false
 )

[jancborchardt]

Follow-up as talked with @ChristophWurst and mentioned above:

It is expected from (the majority of) other clients that "Mark as spam" will also move it to spam/junk.

Meaning the toggle to need to enable this functionality can be removed as it should be enabled by default.

[jancborchardt]

→ #8738