Add Zendesk access-review connector

Zendesk is a multi-tenant OAuth connector keyed by the customer
subdomain. The customer enters it at connect time; it rides the signed
state to the callback, is re-validated, and is stored on the connector
settings to build the API host.

List staff (agents and admins) via GET /api/v2/users.json with cursor
pagination, mapping role, active/suspended, and 2FA status; end-users
are excluded. The subdomain is validated as a single DNS label at every
trust boundary to close the SSRF vector, and the data client keeps the
SSRF-protected transport.

Zendesk OAuth across customer subdomains requires a Zendesk-approved
global OAuth client; the connector goes live once those credentials are
supplied via bootstrap.

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

pkg/coredata/connector_provider.go

@@ -59,6 +59,7 @@ const (
 	ConnectorProviderCursor       ConnectorProvider = "CURSOR"
 	ConnectorProviderDatadog      ConnectorProvider = "DATADOG"
 	ConnectorProviderOkta         ConnectorProvider = "OKTA"
+	ConnectorProviderZendesk      ConnectorProvider = "ZENDESK"
 )
 
 var (
@@ -105,6 +106,7 @@ func ConnectorProviders() []ConnectorProvider {
 		ConnectorProviderCursor,
 		ConnectorProviderDatadog,
 		ConnectorProviderOkta,
+		ConnectorProviderZendesk,
 	}
 }
 
@@ -146,7 +148,8 @@ func (v ConnectorProvider) IsValid() bool {
 		ConnectorProviderAnthropic,
 		ConnectorProviderCursor,
 		ConnectorProviderDatadog,
-		ConnectorProviderOkta:
+		ConnectorProviderOkta,
+		ConnectorProviderZendesk:
 		return true
 	}