Find a way to autogenerate migrations outside of app context

[reginafcompton]

This repo operates outside of a current_app context. However, the alembic env script derives values from the app context, and thus, most basic alembic commands (e.g., autogenerate) cannot run without a corresponding app.

mci-database/mci_database/db/migrations/env.py

Lines 24 to 27 in 7351a0b

	from flask import current_app
	config.set_main_option('sqlalchemy.url',
	current_app.config.get('SQLALCHEMY_DATABASE_URI'))
	target_metadata = current_app.extensions['migrate'].db.metadata

The alembic docs suggest that the env.py file can be "hacked" or modified to meet your needs. Let's adjust the env.py file, so we can autogenerate migrations outside of an app context, something like:

mci-database/mci_database/db/alembic/env.py

Lines 20 to 34 in c4532db

	# Helper variable to indicate that Alembic is operating outside of an app context.
	is_offline = False
	# add your model's MetaData object here
	# for 'autogenerate' support
	# from myapp import mymodel
	# target_metadata = mymodel.Base.metadata
	from flask import current_app
	try:
	config.set_main_option('sqlalchemy.url',
	current_app.config.get('SQLALCHEMY_DATABASE_URI'))
	target_metadata = current_app.extensions['migrate'].db.metadata
	except RuntimeError as e:
	is_offline = True