feat: PostgresProvider - Add POSTGRES_URL_OVERRIDE

[tba-code]

What type of PR is this?

• bug
• cleanup
• documentation
• feature

What this PR does / why we need it:

• Added POSTGRES_URL to PostgresProvider as an override for the individual POSTGRES_* variables currently in use.
• PostgresProvider.db_url no longer rebuilds the db url on every call.
• Updated the documentation to reflect the new variable and it's usage.
• The override can be used to specify a UNIX socket for postgres.

Which issue(s) this PR fixes:

Fixes #3392

Testing

1). Installed postgres locally into a mealie devcontainer.
2). Created a database for mealie
3). Tested multiple values of POSTGRES_URL (omitted, specified using default config, specified using file socket). using task dev:services and task py:postgres for more complete testing.

[hay-kot]

LGTM, will defer to @boc-the-git for merge

[boc-the-git]

I don't like the wording "Must" here - it implies it's mandatory when in fact it's optional.

[tba-code]

It's not optional if using the variable. You must define that or it will not work because the provider is created based on DB_ENGINE.

[boc-the-git]

Yea, I understand the message you're trying to communicate, but I don't agree that the words achieve that. Otherwise that same message should be on all the POSTGRES_x env vars?

Something that talks to what it replaces would make more sense, e.g. (don't quote me, I've given this very little thought!!) "Postgres URL override. Used in place of POSTGRES_x/POSTGRES_y/... if you want to specify the full connection URI"

[tba-code]

This is what I came up with: "Optional Postgres URL override to use instead of POSTGRES_* variables. Must be used in conjunction with DB_ENGINE: postgres to have an effect."

[boc-the-git]

It's absolutely an improvement, I just still find this a weird addition Must be used in conjunction with DB_ENGINE: postgres to have an effect., per previous comments.

[tba-code]

I'd be nervous to not add something similar as this is a quirk of the implementation.

The URL includes the dialect already, so its quite weird to have it specific to postgres if I am honest here.
If you don't specify it must still be used in conjunction with DB_ENGINE: postgres, someone may think that specifying DB_ENGINE is redundant, and remove it, only to find the instance has gone back to sqlite.

[boc-the-git]

Pretend this new variable doesn't exist..
If a user does not specify DB_ENGINE: postgres, they get a sqlite DB already, right?
It looks that way to me, based on https://github.com/mealie-recipes/mealie/blob/mealie-next/mealie/core/settings/settings.py#L215

I'm all for the docs being improved, but adding this exact message, to this one environment variable, adds more confusion rather than simplifying things.

[tba-code]

Changed.

[boc-the-git]

One doco change needed, but otherwise happy for this to be merged - even ahead of the security release if that's how the timing works out. I don't see this as being a risky change given it's a new env var being introduced.

Oh, and I'm crowd sourcing an opinion to the change of how timezone is set in the sample files.. that's on Discord.

[boc-the-git]

👍