Handling users through the DB users table

[vporton]

I changed the DB schema to store users in DB: users table created.

I use now user_ref (int) instead of user_id (VARCHAR) to refer to a user.

In UserInputDto I use pk to refer to the user instead of, as before, his/her email.

I did basic testing and it appears to work, more testing is however needed.

Fixes #6.

[vporton]

Currently, it does not work (Python exceptions).

[vporton]

To be honest, I am a little confused how to rewrite this. I will concentrate on this PR.

[vporton]

It seems that I've finished this PR. It was preliminarily tested and I'd vote to merge it.

[apssouza22]

Looks good. I will test it this weekend.

Thx @vporton

[apssouza22]

After logged in and try to use the UI I got an error. user.pk is None

  commands = await agent.handle_user_input(user_input_req)
  File "/Users/alexsandro.souza/projects/my/chatflow/server/src/core/agent/agent_service.py", line 55, in handle_user_input
    add_message_dto = AddMessageDto(
  File "pydantic/main.py", line 341, in pydantic.main.BaseModel.__init__
pydantic.error_wrappers.ValidationError: 1 validation error for AddMessageDto
user_ref
  none is not an allowed value (type=type_error.none.not_allowed)

[vporton]

After logged in and try to use the UI I got an error. user.pk is None

Fixed.

[apssouza22]

@vporton I will test it and merge if it is working fine