[feature] scheduled statuses (#4274)

An implementation of [`scheduled_statuses`](https://docs.joinmastodon.org/methods/scheduled_statuses/). Will fix #1006.

this is heavily WIP and I need to reorganize some of the code, working on this made me somehow familiar with the codebase and led to my other recent contributions
i told some fops on fedi i'd work on this so i have no choice but to complete it 🤷‍♀️
btw iirc my avatar presents me working on this branch

Signed-off-by: nicole mikołajczyk <git@mkljczk.pl>
Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4274
Co-authored-by: nicole mikołajczyk <git@mkljczk.pl>
Co-committed-by: nicole mikołajczyk <git@mkljczk.pl>

internal/db/bundb/bundb.go

@@ -76,6 +76,7 @@ type DBService struct {
 	db.Relationship
 	db.Report
 	db.Rule
+	db.ScheduledStatus
 	db.Search
 	db.Session
 	db.SinBinStatus
@@ -261,6 +262,10 @@ func NewBunDBService(ctx context.Context, state *state.State) (db.DB, error) {
 			db:    db,
 			state: state,
 		},
+		ScheduledStatus: &scheduledStatusDB{
+			db:    db,
+			state: state,
+		},
 		Search: &searchDB{
 			db:    db,
 			state: state,