subscribe masjid feature

[adsau59]

create "subscribe" table to store info on which user have subscribed to which masjid, and create a database function to fetch that info

need 3 functions (in user context):

• [x] get_subscribed_masjids()
• [x] subscribe_masjid(masjid_id)
• [x] unsubscribe_masjid(masjid_id)

[adsau59]

done