Add db functions

[maihoangbichtram]

• Add update function for session

  Without update func

  old_current_solutions = ( db.query(SolutionArchive) .filter(SolutionArchive.problem == problem_id, SolutionArchive.user == user.index, SolutionArchive.current) .all() )

for old in old_current_solutions: old.current = False

With update func

await db.update( update(SolutionArchive) .where(SolutionArchive.problem==problem_id, SolutionArchive.current==True) .values(current=False) )

• Make use of scopefunc (async_scoped_session). By using current_task as scopefunc, a new session will be created for each new coroutine. -> To avoid coroutine issue
• Separate sessions for different requests to API

[juropo]

Can you explain what the purpose of these changes is?

[maihoangbichtram]

Instead of fetching all records and update each record with desired value, I call only 1 update function to update the values that matches the filter conditions.

Each call to API will now there its own db session, instead of 1 db session for all calls to API.

[maihoangbichtram]

PR reconstruct