dbox: Initialize pop3-uidl header on INBOX creation.

This way we don't add any UIDLs to dovecot.index.cache on the first POP3
UIDL access. We'll assume that pop3-uidl header is updated whenever any
backend UIDLs are added, which should happen nowadays.

src/lib-storage/index/dbox-multi/mdbox-storage.c

@@ -9,6 +9,7 @@
 #include "mail-index-alloc-cache.h"
 #include "mailbox-log.h"
 #include "mailbox-list-private.h"
+#include "index-pop3-uidl.h"
 #include "dbox-mail.h"
 #include "dbox-save.h"
 #include "mdbox-map.h"
@@ -309,6 +310,9 @@ mdbox_write_index_header(struct mailbox *box,
 	}
 	mail_index_view_close(&view);
 
+	if (box->inbox_user)
+		index_pop3_uidl_set_max_uid(box, trans, 0);
+
 	mdbox_update_header(mbox, trans, update);
 	if (new_trans != NULL) {
 		if (mail_index_transaction_commit(&new_trans) < 0) {

src/lib-storage/index/dbox-single/sdbox-storage.c

@@ -6,6 +6,7 @@
 #include "mail-index-modseq.h"
 #include "mail-search-build.h"
 #include "mailbox-list-private.h"
+#include "index-pop3-uidl.h"
 #include "dbox-mail.h"
 #include "dbox-save.h"
 #include "sdbox-file.h"
@@ -262,6 +263,9 @@ int sdbox_mailbox_create_indexes(struct mailbox *box,
 						 update->min_highest_modseq);
 	}
 
+	if (box->inbox_user)
+		index_pop3_uidl_set_max_uid(box, trans, 0);
+
 	sdbox_update_header(mbox, trans, update);
 	if (new_trans != NULL) {
 		if (mail_index_transaction_commit(&new_trans) < 0) {