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/better_stack.go

@@ -38,10 +38,11 @@ import (
 // name that scopes the team-members listing.
 func betterStackRegistration() *Registration {
 	return &Registration{
-		Provider:       coredata.ConnectorProviderBetterStack,
-		DisplayName:    "Better Stack",
-		SupportsAPIKey: true,
-		ProbeURL:       "https://betterstack.com/api/v2/team-members",
+		Provider:         coredata.ConnectorProviderBetterStack,
+		DisplayName:      "Better Stack",
+		DocumentationURL: accessReviewDocsURL("better-stack"),
+		SupportsAPIKey:   true,
+		ProbeURL:         "https://betterstack.com/api/v2/team-members",
 		APIKeyExtraSettings: []ExtraSetting{
 			{Key: "teamName", Label: "Team Name", Required: true},
 		},