fix: correctly send links to login v2 in email notifications (#10711)

# Which Problems Are Solved

There were still some emails (passkey registration and domain claimed)
sent with links pointing to login v1 even when the login v2 was enabled
for the instance.
Also while looking into the issue, it was discovered that some links
pointing to login V2 were not correctly generated.


# How the Problems Are Solved

- Added default paths for passkey registration and domain claimed
notifications
- Fixed the existing paths to properly handle concatenation (resp. use
`url.ResolveReference`)
  - Change their go types (from string) to `*url.URL` 
  - Added a mapstructure hook for string to url
- Removed unnecessary `InstanceSetupFeatures` and corresponding
conversions
- Refactored the methods on the `login.DefaultPaths` struct and added an
interface to the `Commands` to only need to pass a single config (and
not every method)
- Added an `OriginURL` method to the `DomainCtx` to prevent going from
url to string and back
- Added the use of the templates in case of enabled login v2 for passkey
registration and domain claimed)

# Additional Changes

None

# Additional Context

closes #10643

---------

Co-authored-by: Max Peintner <[email protected]>
Co-authored-by: Livio Spring <[email protected]>
Co-authored-by: Livio Spring <[email protected]>
Co-authored-by: Max Peintner <[email protected]>
Co-authored-by: Gayathri Vijayan <[email protected]>

cmd/setup/setup.go

@@ -186,6 +186,7 @@ func Setup(ctx context.Context, config *Config, steps *Steps, masterKey string)
 	steps.FirstInstance.externalDomain = config.ExternalDomain
 	steps.FirstInstance.externalSecure = config.ExternalSecure
 	steps.FirstInstance.externalPort = config.ExternalPort
+	steps.FirstInstance.defaultPaths = config.Login.DefaultPaths
 
 	steps.s5LastFailed = &LastFailed{dbClient: dbClient.DB}
 	steps.s6OwnerRemoveColumns = &OwnerRemoveColumns{dbClient: dbClient.DB}
@@ -573,9 +574,7 @@ func startCommandsQueries(
 		config.OIDC.DefaultRefreshTokenExpiration,
 		config.OIDC.DefaultRefreshTokenIdleExpiration,
 		config.DefaultInstance.SecretGenerators,
-
-		nil,
-		nil,
+		config.Login.DefaultPaths,
 	)
 	logging.OnError(ctx, err).Fatal("unable to start commands")
 
@@ -599,7 +598,7 @@ func startCommandsQueries(
 		commands,
 		queries,
 		eventstoreClient,
-		config.Login.DefaultPaths.OTPEmailPath,
+		config.Login.DefaultPaths.DefaultOTPEmailURLTemplate,
 		config.SystemDefaults.Notifications.FileSystemPath,
 		keys.User,
 		keys.SMTP,