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/coredata/connector_settings.go

@@ -194,6 +194,25 @@ type (
 	CrispConnectorSettings struct {
 		WebsiteID string `json:"website_id"`
 	}
+
+	// SegmentConnectorSettings stores the Twilio Segment Public API base URL.
+	// A Public API token is bound to one workspace, but the workspace's region
+	// is not discoverable from the token and selects the API host
+	// (api.segmentapis.com for US, eu1.api.segmentapis.com for EU). The region
+	// the customer picks is resolved to this base URL up front, so the driver
+	// and probe read a single host with no region logic.
+	SegmentConnectorSettings struct {
+		BaseURL string `json:"base_url"`
+	}
+
+	// GoogleAnalyticsConnectorSettings stores the selected GA4 account ID
+	// (the numeric portion of the `accounts/{account}` resource name). A
+	// Google OAuth token can reach many GA4 accounts, so the reviewed account
+	// is picked after authorization; the driver then lists the account's
+	// access bindings plus the bindings of every property beneath it.
+	GoogleAnalyticsConnectorSettings struct {
+		AccountID string `json:"account_id"`
+	}
 )
 
 // GrantType returns the OAuth2 grant type recorded on the connector's