Refactor create_app in airflow/www/app.py

[mik-laj]

This function was too long. It was very difficult to trace how it works. I divided it into 15 functions in 7 modules, which I am sure will facilitate its development. This file was also excluded from pylint_todo, so I fixed it to prevent regression.

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[kaxil]

Suggested change

	Add X-Frame-Options header. Use it avoid click-jacking attacks, by ensuring that their content is not
	Add X-Frame-Options header. Use it to avoid click-jacking attacks, by ensuring that their content is not

[mik-laj]

Thanks. Fixed 🐈

[kaxil]

It is just used at 2 places so I think the following might be better, WDYT?

Suggested change

	from airflow.www.api.experimental import endpoints as e
	# required for testing purposes otherwise the module retains
	# a link to the default_auth
	if app.config['TESTING']:
	import importlib
	importlib.reload(e)
	app.register_blueprint(e.api_experimental, url_prefix='/api/experimental')
	app.extensions['csrf'].exempt(e.api_experimental)
	from airflow.www.api.experimental import endpoints
	# required for testing purposes otherwise the module retains
	# a link to the default_auth
	if app.config['TESTING']:
	import importlib
	importlib.reload(endpoints)
	app.register_blueprint(e.api_experimental, url_prefix='/api/experimental')
	app.extensions['csrf'].exempt(endpoints.api_experimental)

[mik-laj]

Agree. We don't need an alias here.

[kaxil]

2 minor comments

[mik-laj]

@kaxil Fixed. Thank you so much for the quick review.