Add default alias name to custom domain

[SibrenVasse]

Implementation for https://trello.com/c/dz9npgnw/66-able-to-set-alias-name-for-a-domain

The name in the from header is first set by the alias name, then the default alias name from the domain and otherwise not present.

Implementation runtime tested. I'm not sure if I did the migration correctly, as I could not find any documentation on this. I did my best to try and follow a similar style to the rest of the codebase. Let me know what you think.

[nguyenkims]

Overall the PR is perfect! I just left some rather nitpicking comments :).

[nguyenkims]

We can use alias.custom_domain_id here I think. This field is filled up if the alias is dynamically created thanks to the directory feature.

We can also create a relationship like custom_domain = db.relationship("CustomDomain", foreign_keys=[custom_domain_id]) to avoid doing a CustomDomain.get(), this is the same in terms of number of query to the database though.

[SibrenVasse]

I ended up adding the relationship in the model, this enabled me to display the domain-wide alias name as a placeholder in the alias view.

This does make alias.custom_domain_id redundant, but it has quite a few users left.

[nguyenkims]

@SibrenVasse Thanks a lot for the PR!

For the database migration, this requires having a Postgres database indeed. On local environment, a sqlite database is created by the db.create_all() that bypasses the migration. This is convenient for development and unit tests as we don't have to wait for the migration.

If you have docker, you can create the migration by the following command: it first creates a postgres database for SimpleLogin, then run flask db upgrade to upgrade the DB to the latest stage and finally flask db migrate to generate the migration script. Let me know if this makes sense :).

docker rm -f sl-db
docker run -p 5432:5432 --name sl-db -e POSTGRES_PASSWORD=postgres -e POSTGRES_DB=sl -d postgres

env DB_URI=postgresql://postgres:postgres@127.0.0.1:5432/sl flask db upgrade

env DB_URI=postgresql://postgres:postgres@127.0.0.1:5432/sl flask db migrate

docker rm -f sl-db

[SibrenVasse]

The migration (up and down) ran successfully with your instructions.

[SibrenVasse]

I've resolved your comments.

[nguyenkims]

@SibrenVasse perfect, thanks a lot! We'll test on staging and then deploy onto production today or tomorrow.