imap-urlauth: Allow connections from services other than IMAP. The imap-urlauth service detects the new submission service and assigns the appropriate privileges. The dovecot-token authentication mechanism provides information on which service connected to it.

Changed type of internet port values to in_port_t everywhere. Created special SET_IN_PORT setting type for internet port values. Created net_str2port() for parsing internet port values. Removed several atoi() invocations in the process.

imap-urlauth: Store urlauth keys to the new mailbox attributes.

imap-urlauth: Fixes to handling anonymous user

Added support for IMAP URLAUTH and URLAUTH=BINARY extensions Extends imap service with URLAUTH and URLAUTH=BINARY support: - Adds new commands URLFETCH, GENURLAUTH and RESETKEY. Creates imap-urlauth service in src/imap-urlauth. Functionality common to both the imap and imap-urlauth services is located in src/lib-imap-urlauth. TODO: - use mailbox GUIDs instead of names - doveadm command to delete stale urlauth entries? - add delay when attempting to access nonexistent user - create urlauth-worker queue, similar to how indexer-worker works (could we share code?..)