PoC: Investigate support for database

[tchaton]

What does this PR do?

This PR explores SQModel integration within the Lightning App framework to simplify database manipulation.

# Why SQModel

From Sebastián Ramírez, SQLModel removes boilerplate to interact with database from Python. Its SQLModel is a SQLAlchemy model and a Pydantic model ✨ Which makes it very easy to use with FastAPI.

My personal opinion is that it removes most of the boilerplate to manipulate the specs from control-plane to data plane and reconciliation.

https://user-images.githubusercontent.com/12861981/183063574-63e517ed-009b-4adc-b920-9dc3d815ac35.mov

https://user-images.githubusercontent.com/12861981/183063620-8bc5cc6b-7483-4ba1-a0e4-819e48613c84.mov

Another benefit is the ease to access reading and writing from / to the database for the users.

Reading

class FlowDB(LightningFlow):

    def run(self):
        if self.schedule("...."):
                 self.read_from_db()

   def read_from_db(self):
        with Session(self.engine) as session:
              ....
              return ...

Writing to the DB through the Rest API

Associated with the configure_api PR https://github.com/Lightning-AI/lightning/pull/13945, you get full pydantic validation + database entries.

class FlowDB(LightningFlow):

    def run(self):
        if self.schedule("...."):
                 self.read_from_db()

   def something_handler(self, config: SomethingConfig):
        with Session(self.engine) as session:
              ....
              return ...

   def configure_api(self):
         return [Post("/create_something", self.something_handler)

Fixes #<issue_number>

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[justusschock]

@tchaton is this still relevant or can this be closed? Research Studio does have databases, right?