Support LevelAlias names in configuration parsing

[mohammed-saalim]

Fixes #461

Summary

Updates ParseLogEventLevel() in ConfigurationReader.cs to accept LevelAlias values (Off, Minimum, Maximum) before attempting to parse as LogEventLevel enum.
This allows users to set "MinimumLevel": "Off" in appsettings.json to completely disable logging, which previously failed with:

InvalidOperationException: The value Off is not a valid Serilog level.

Changes

• Modified ParseLogEventLevel() method to check for LevelAlias names first
• Handles "Off", "Minimum", and "Maximum" (case-insensitive)
• Falls back to enum parsing for standard log levels (Verbose, Debug, Information, etc.)

Testing

• ✅ All existing tests pass (1191/1191)
• ✅ Manual testing confirmed "MinimumLevel": "Off" works from configuration
• ✅ Build successful across all target frameworks

This follows the guidance from @nblumhardt in the issue thread.

[nblumhardt]

This looks good, thanks. Would it be possible to add one small test (i.e. an xUnit theory) that checks ParseLogEventLevel still handles the original values, plus the expected new ones? It will be necessary to mark ParseLogEventLevel as internal for this.

[mohammed-saalim]

Done! Added tests as requested. All pass locally. @nblumhardt

[nblumhardt]

Great! Thanks @mohammed-saalim 👍

[tvardero]

@mohammed-saalim @nblumhardt should json schema for appsettings.json be updated as well?
For intellisense / autocompletion.

I know Rider has it for Serilog, but i'm not sure where it gets it.

[nblumhardt]

Great suggestion, thanks; I'm not sure where this comes from either - a PR would be welcome if anyone has a chance to figure it out :-)

[Numpsy]

Is that the one linked from #404? e.g. https://github.com/SchemaStore/schemastore/blob/e24defd47bd4942d34a363d4ff09efe0a8cbfeea/src/schemas/json/appsettings.json#L808

(Ithink that' what VCode uses anyway)

[tvardero]

Is that the one linked from #404?

@Numpsy, indeed it was!
I have made a PR to schemastore, it was already merged and level "Off" is not being suggested in Rider.

Thank you

[tvardero]

@nblumhardt Sorry to rush, but can this be released as patch?

[bartelink]

@tvardero the PR got merged into dev, which triggers an auto-publish of a -dev prerelease; see https://www.nuget.org/packages/serilog.settings.configuration

Standard protocol is for the developer and/others to take it for a spin and validate (commenting or raising an issue if there are any anomalies), and then it's included in the next non-preview release (which is off master)