Register Anthropic access-review connector

Add the ANTHROPIC connector_provider enum value, its migration, and the
GraphQL enum binding, then register the provider as an API-key connector
that authenticates via x-api-key.

The probe URL is left empty because the shared connection probe cannot
send the required anthropic-version header and would misreport a valid
key; a dead key surfaces on the first member fetch instead.

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

pkg/connector/provider/builtin.go

@@ -22,6 +22,7 @@ package provider
 func NewBuiltinRegistry() *Registry {
 	r := NewRegistry()
 	for _, reg := range []*Registration{
+		anthropicRegistration(),
 		asanaRegistration(),
 		bitbucketRegistration(),
 		brexRegistration(),