Optimization: move email templates from site.config to it's own field

[nlsvgtr]

It would be nice to move email templates from the site config to a new field.

site.config is a json field with a lot of data. All this data is requested from the database again and again.

The email templates are currently stored in site.config. This means that these templates are also requested from the database again and again. But this data is hardly ever used.

Moving these templates to another field in the site table, and only request those fields when required, would significantly reduce ttraffic between the API and database server, and between the API and the frontend server.