[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>

example/config.yaml

@@ -520,9 +520,7 @@ instance-stats-mode: ""
 
 # Bool. This flag controls whether local accounts may backdate statuses
 # using past dates with the scheduled_at param to /api/v1/statuses.
-# This flag does not affect scheduling posts in the future
-# (which is currently not implemented anyway),
-# nor can it prevent remote accounts from backdating their own statuses.
+# This flag can't prevent remote accounts from backdating their own statuses.
 #
 # If true, all local accounts may backdate statuses.
 # If false, status backdating will be disabled and an error will be returned if it's used.
@@ -870,6 +868,16 @@ statuses-poll-option-max-chars: 50
 # Default: 6
 statuses-media-max-files: 6
 
+# Int. Maximum number of statuses a user can schedule at time.
+# Examples: [300]
+# Default: 300
+scheduled-statuses-max-total: 300
+
+# Int. Maximum number of statuses a user can schedule for a single day.
+# Examples: [25]
+# Default: 25
+scheduled-statuses-max-daily: 25
+
 ##############################
 ##### LETSENCRYPT CONFIG #####
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