Add Google Analytics, Dotfile, Segment and Square access-review connectors

Two OAuth2 and two API-key connectors:

- Google Analytics (GA4): OAuth2 with both analytics.readonly and
  analytics.manage.users.readonly (readonly alone 403s on the accounts
  list); v1alpha accessBindings enumerated at account and property level
  and merged by email; manual account picker (Pattern 1) with a
  per-connection probe and name resolver; distinct from Google Workspace.
- Dotfile: API key in the X-DOTFILE-API-KEY header (Pattern 3); GET
  /v1/users (owner/admin, suspended_at) with a static probe.
- Segment (Twilio): Public API token as Bearer with a required Region
  setting (US or EU) mapped to the regional host; GET /users plus per-user
  GET /users/{id} for roles and /invites for pending members; per-connection
  BuildProbeURL.
- Square: OAuth2 (EMPLOYEES_READ) or a personal access token (Pattern 3);
  POST /v2/team-members/search returns email/status/is_owner directly, so no
  role resolution; custom probe and name resolver.

Google Analytics and Square are confidential OAuth clients, wired into the
bootstrap OAuth provider list and .env.example. Segment carries a required
extra setting, so the console add-source dialog maps region onto its
segmentRegion API-key input; without that mapping the value is silently
dropped and the create is rejected.

Cassette-backed driver tests plus unit tests for the Segment probe URL and
the bootstrap OAuth provider list.

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

pkg/accessreview/drivers/testdata/square.yaml

@@ -0,0 +1,39 @@
+---
+# Hand-authored cassette for POST /v2/team-members/search (Square, Bearer token
+# stripped by the recorder). No query filter is sent, so the request body is the
+# minimal {"limit":200}; an absent response cursor terminates pagination. Three
+# synthetic team members cover owner/non-owner and ACTIVE/INACTIVE. The
+# team_member shape (id, is_owner, status, given_name, family_name,
+# email_address, created_at) mirrors the SearchTeamMembers response.
+version: 2
+interactions:
+    - id: 0
+      request:
+        proto: HTTP/1.1
+        proto_major: 1
+        proto_minor: 1
+        content_length: 13
+        host: connect.squareup.com
+        body: '{"limit":200}'
+        headers:
+            Accept:
+                - application/json
+            Content-Type:
+                - application/json
+            Square-Version:
+                - "2026-05-20"
+        url: https://connect.squareup.com/v2/team-members/search
+        method: POST
+      response:
+        proto: HTTP/2.0
+        proto_major: 2
+        proto_minor: 0
+        content_length: -1
+        uncompressed: true
+        body: '{"team_members":[{"id":"-3oZQKPKVk6gUXU_V5Qa","is_owner":false,"status":"ACTIVE","given_name":"Sherlock","family_name":"Holmes","email_address":"sherlock.holmes@example.com","created_at":"2020-03-24T18:14:26Z"},{"id":"Pw67AzUomYUdF04AN17i","is_owner":true,"status":"ACTIVE","given_name":"John","family_name":"Watson","email_address":"john.watson@example.com","created_at":"2020-03-24T18:14:26Z"},{"id":"Xk92LmQ0pRsTuvWxYz01","is_owner":false,"status":"INACTIVE","given_name":"Martha","family_name":"Hudson","email_address":"martha.hudson@example.com","created_at":"2021-06-10T09:00:00Z"}]}'
+        headers:
+            Content-Type:
+                - application/json
+        status: 200 OK
+        code: 200
+        duration: 100ms