Add five API-key access-review connectors

Add Mercury, Apollo.io, Deepgram, ClickHouse Cloud, and Langfuse as
access-review connectors. All are API-key, single-tenant providers
(Pattern 3): the key identifies one tenant, so there is no OAuth flow,
picker UI, or bootstrap/helm configuration.

- Mercury: Bearer token, GET /api/v1/users, cursor pagination.
- Apollo.io: x-api-key header, GET /api/v1/users/search (teammates).
- Deepgram: Token scheme; lists members across every project and
  dedupes by member_id, unioning per-project scopes.
- ClickHouse Cloud: HTTP Basic (keyId:keySecret); discovers the org
  via GET /v1/organizations, then lists its members.
- Langfuse: HTTP Basic (publicKey:secretKey); a base-URL setting
  selects the regional cloud host or a self-hosted instance.

Each adds the enum value, migration, GraphQL binding, provider
Registration, a driver with a cassette-driven test, and a brand logo.

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

pkg/connector/provider/builtin.go

@@ -23,15 +23,18 @@ func NewBuiltinRegistry() *Registry {
 	r := NewRegistry()
 	for _, reg := range []*Registration{
 		anthropicRegistration(),
+		apolloRegistration(),
 		asanaRegistration(),
 		betterStackRegistration(),
 		bitbucketRegistration(),
 		brexRegistration(),
 		clerkRegistration(),
+		clickhouseRegistration(),
 		clickupRegistration(),
 		cloudflareRegistration(),
 		cursorRegistration(),
 		datadogRegistration(),
+		deepgramRegistration(),
 		docusignRegistration(),
 		grafanaRegistration(),
 		githubRegistration(),
@@ -40,7 +43,9 @@ func NewBuiltinRegistry() *Registry {
 		herokuRegistration(),
 		hubspotRegistration(),
 		intercomRegistration(),
+		langfuseRegistration(),
 		linearRegistration(),
+		mercuryRegistration(),
 		metabaseRegistration(),
 		microsoft365Registration(),
 		mondayRegistration(),