fix: Enable OIDC with Synology SSO Server

[JoTec2002]

What type of PR is this?

(REQUIRED)

• feature
• bug

What this PR does / why we need it:

Mealie required the name claim from an OIDC Provider, but the Synology SSO Server doesn't Provide this claim.

After this Pull Request Mealie will no longer required the name claim to be present.

To not cause any issues or lose any OIDC user information the following logic is used:
If the name claim is present it will be used, otherwise the username will be used as name.

Which issue(s) this PR fixes:

Fixes #4543

[MuadDibVV]

+1

[cmintey]

I think it would be better and more extensible to introduce a new env var OIDC_NAME_CLAIM, which would default to name, but you could override it to whatever you want.

[michael-genson]

@JoTec2002 if you could take a look at the feedback from @cmintey we should be able to get this merged!

[JoTec2002]

@cmintey I completed the changes you suggested.

[cmintey]

Looking good! One more small thing to address

[cmintey]

Thanks for working on this!