Add option to choose postgres during installation

[ghost]

No description provided.

[richvdh]

When we come to do this, dbconfig-common looks like it might provide some help to do the debian side of it.

[richvdh]

I'm not really clear what this is asking for. There's nothing stopping you using postgres during installation today. Is it just a matter of better documentation?

[aaronraimist]

What I am envisioning is a interactive step during the configuration generation process where it explains to you that there are two choices for database engines, explains why you would want Postgres, and then gives you an option to generate the config with Postgres configured in homeserver.yaml.

[ptman]

@aaronraimist is it possible to install postgres after that question?

[aaronraimist]

I assume so. (I don't know how this would work technically, I'm just speaking as a user).

I guess it could either

1. generate the config file with spots for you to fill in your Postgres connection details so you can install Postgres and fill that in after Synapse is installed or
2. it could install Postgres for you if you are using the Debian package or similar or
3. it could let you back out, install Postgres, and come back to this step and have you type in the connection details interactively and then it would plug those in to the config