Link the 19 API-key access-review connector docs

Each of these providers ships an API-key connection path and a driver, but
no Registration carried a DocumentationURL, so the console rendered no
"how do I get this token" link on the connect dialog. probo.com now has a
page per provider, so point each Registration at it.

Slugs are passed explicitly rather than derived from the enum, per
accessReviewDocsURL's contract, so BETTER_STACK maps to better-stack and
INCIDENT_IO to incident-io.

Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>

pkg/connector/provider/langfuse.go

@@ -34,9 +34,10 @@ import (
 
 func langfuseRegistration() *Registration {
 	return &Registration{
-		Provider:       coredata.ConnectorProviderLangfuse,
-		DisplayName:    "Langfuse",
-		SupportsAPIKey: true,
+		Provider:         coredata.ConnectorProviderLangfuse,
+		DisplayName:      "Langfuse",
+		DocumentationURL: accessReviewDocsURL("langfuse"),
+		SupportsAPIKey:   true,
 		// Langfuse's organization-scoped public API authenticates with HTTP
 		// Basic auth where the credential is publicKey:secretKey.
 		// APIKeyBasicAuthUserPass base64s the verbatim "publicKey:secretKey" the