fix: load settings for valid user and email check (#6674)

- The doctor commands to check the validity of existing usernames and
email addresses depend on functionality that have configurable behavior
depending on the values of the `[service]` settings, so load them when
running the doctor command.
- Resolves #6664
- No unit test due to the architecture of doctor commands.

# Testing

1. Set `[service].ALLOW_DOTS_IN_USERNAMES = true`.
2. Create a user that contains a dot in their username.
3. Run the `check-user-name` doctor command and verify there's no error reported.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/6674
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>

modules/setting/service.go

@@ -140,6 +140,11 @@ func CompileEmailGlobList(sec ConfigSection, keys ...string) (globs []glob.Glob)
 	return globs
 }
 
+// LoadServiceSetting loads the service settings
+func LoadServiceSetting() {
+	loadServiceFrom(CfgProvider)
+}
+
 func loadServiceFrom(rootCfg ConfigProvider) {
 	sec := rootCfg.Section("service")
 	Service.ActiveCodeLives = sec.Key("ACTIVE_CODE_LIVE_MINUTES").MustInt(180)