DOC: Deploy on Azure

[roldengarm]

Very good documentation on how to deploy to Azure! There are two things I would like to add:

• Fider doesn't seem compatible with Postgres Flexible Server (out of the box). The Azure Portal suggests to use Flexible Server instead of Single Server, which I did. But then the app fails on startup with: pq: extension "pg_trgm" is not allow-listed for "azure_pg_admin" users in Azure Database for PostgreSQL
  Looks like this extension is indeed not available
• Another app setting is required HOST_DOMAIN which is not in the documentation. After adding it, it works.

[goenning]

Did it work on Single Server? We might need to change the docs.

The HOST_DOMAIN is no longer needed on the latest version (not released yet), so that's why there is a mismatch! I'll likely release it this week to avoid further confusion.

[roldengarm]

@goenning yes it worked on Single Server. All good now.

Thanks!