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/accessreview/drivers/testdata/langfuse.yaml

@@ -0,0 +1,32 @@
+---
+# Hand-authored fixture for GET /api/public/organizations/memberships against a
+# Langfuse organization (org-scoped API key). The membership object shape
+# (userId, role, email, name) and the {memberships:[...]} wrapper mirror the
+# documented response. Synthetic IDs/emails only.
+version: 2
+interactions:
+    - id: 0
+      request:
+        proto: HTTP/1.1
+        proto_major: 1
+        proto_minor: 1
+        content_length: 0
+        host: cloud.langfuse.com
+        headers:
+            Accept:
+                - application/json
+        url: https://cloud.langfuse.com/api/public/organizations/memberships
+        method: GET
+      response:
+        proto: HTTP/2.0
+        proto_major: 2
+        proto_minor: 0
+        content_length: -1
+        uncompressed: true
+        body: '{"memberships":[{"userId":"lf-user-1","role":"OWNER","email":"owner@example.com","name":"Olivia Owner"},{"userId":"lf-user-2","role":"ADMIN","email":"admin@example.com","name":"Adam Admin"},{"userId":"lf-user-3","role":"MEMBER","email":"member@example.com","name":"Mia Member"},{"userId":"lf-user-4","role":"VIEWER","email":"viewer@example.com","name":""}]}'
+        headers:
+            Content-Type:
+                - application/json
+        status: 200 OK
+        code: 200
+        duration: 100ms