documentation: Database migration step not clear in developer docs

[Ankush-Chander]

Describe the bug
I am following developer setup link and upon running

python -m argilla

I am getting following error:

INFO:     Started server process [3208]
INFO:     Waiting for application startup.
ERROR:    Traceback (most recent call last):
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1965, in _exec_single_context
    cursor, str_statement, effective_parameters, context
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/engine/default.py", line 748, in do_execute
    cursor.execute(statement, parameters)
sqlite3.OperationalError: no such table: users

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/starlette/routing.py", line 671, in lifespan
    async with self.lifespan_context(app):
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/starlette/routing.py", line 566, in __aenter__
    await self._router.startup()
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/starlette/routing.py", line 648, in startup
    await handler()
  File "/media/disk2/ANKUSH/nlp_repos/argilla/src/argilla/server/server.py", line 231, in log_default_user_warning_if_present
    default_user = accounts.get_user_by_username(db, DEFAULT_USERNAME)
  File "/media/disk2/ANKUSH/nlp_repos/argilla/src/argilla/server/contexts/accounts.py", line 87, in get_user_by_username
    return db.query(User).filter_by(username=username).first()
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/orm/query.py", line 2752, in first
    return self.limit(1)._iter().first()  # type: ignore
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/orm/query.py", line 2858, in _iter
    execution_options={"_sa_orm_load_options": self.load_options},
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 2235, in execute
    _add_event=_add_event,
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 2130, in _execute_internal
    conn,
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/orm/context.py", line 254, in orm_execute_statement
    statement, params or {}, execution_options=execution_options
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1417, in execute
    execution_options or NO_OPTIONS,
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/sql/elements.py", line 487, in _execute_on_connection
    self, distilled_params, execution_options
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1648, in _execute_clauseelement
    cache_hit=cache_hit,
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1843, in _execute_context
    dialect, context, statement, parameters
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1984, in _exec_single_context
    e, str_statement, effective_parameters, cursor, context
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 2326, in _handle_dbapi_exception
    raise sqlalchemy_exception.with_traceback(exc_info[2]) from e
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/engine/base.py", line 1965, in _exec_single_context
    cursor, str_statement, effective_parameters, context
  File "/media/disk2/ANKUSH/nlp_repos/argilla_setup/lib/python3.7/site-packages/sqlalchemy/engine/default.py", line 748, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such table: users
[SQL: SELECT users.id AS users_id, users.first_name AS users_first_name, users.last_name AS users_last_name, users.username AS users_username, users.role AS users_role, users.api_key AS users_api_key, users.password_hash AS users_password_hash, users.inserted_at AS users_inserted_at, users.updated_at AS users_updated_at 
FROM users 
WHERE users.username = ?
 LIMIT ? OFFSET ?]
[parameters: ('argilla', 1, 0)]
(Background on this error at: https://sqlalche.me/e/20/e3q8)

ERROR:    Application startup failed. Exiting.

I was able to get past this error by running following command(although I am not sure if this is the right way to setup fresh database):

python3 -m argilla.tasks.database.migrate

To Reproduce
Steps to reproduce the behavior:

1. Follow instructions mentioned here

Expected behavior
DB setup needs to be added in documentation. Also we can point the developer to Elasticsearch setup in case user hasn"t done it already.

Screenshots
If applicable, add screenshots to help explain your problem.

Environment (please complete the following information):

• OS [e.g. iOS]:
• Browser [e.g. chrome, safari]:
• Argilla Version [e.g. 1.0.0]:
• ElasticSearch Version [e.g. 7.10.2]:
• Docker Image (optional) [e.g. argilla:v1.0.0]:

Additional context
Add any other context about the problem here.

[jfcalvo]

@Ankush-Chander thanks for creating the issue. I have created a PR adding the missing step here: #2613

[Ankush-Chander]

Hi @jfcalvo
Thanks for taking it up swiftly.

I was wondering if we can also add link to elasticsearch setup in the same doc.

So it can be broken into 3 steps:

1. Database setups
   sqlite and elasticsearch
2. Server setup (from source)
3. frontend setup (via bash)

[jfcalvo]

@Ankush-Chander I have tried to apply your feedback on #2613

Please feel free to open a new issue if you think something can be improved. Thanks.