Deduplicate connector driver request helpers

The Crisp and Railway connectors each repeated their HTTP plumbing
across the driver, the name resolver, and (for Crisp) the subscription
settings fetcher: the same JoinPath/headers/Do for Crisp GETs and the
same marshal/POST/headers for Railway GraphQL. The Crisp and Scaleway
drivers also carried byte-identical owner/member role mapping and admin
checks.

Extract crispGet and railwayPost as package-private request helpers so
each call site owns only status handling, and lift the owner/member role
mapping into shared ownerMemberRoles/isOwnerRole helpers beside
activeFromStatus in driver.go. Name the Crisp base URL and tier header
as consts in probe.go's const block rather than inlining the literals,
matching the file's existing convention. Behavior is unchanged.

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

pkg/connector/provider/probe.go

@@ -40,6 +40,9 @@ const (
 	posthogOrganizationPath   = "/api/organizations/@current/"
 	posthogUSBaseURL          = "https://us.posthog.com"
 	posthogEUBaseURL          = "https://eu.posthog.com"
+	crispAPIBaseURL           = "https://api.crisp.chat/v1"
+	crispTierHeader           = "X-Crisp-Tier"
+	crispTierValue            = "plugin"
 )
 
 // ProbeConnection verifies that the connector credential is accepted by the
@@ -505,7 +508,7 @@ func probeCrisp(
 		return fmt.Errorf("missing crisp website_id")
 	}
 
-	endpoint, err := url.JoinPath("https://api.crisp.chat/v1", "website", url.PathEscape(s.WebsiteID), "operators", "list")
+	endpoint, err := url.JoinPath(crispAPIBaseURL, "website", url.PathEscape(s.WebsiteID), "operators", "list")
 	if err != nil {
 		return fmt.Errorf("cannot build crisp probe URL: %w", err)
 	}
@@ -516,7 +519,7 @@ func probeCrisp(
 	}
 
 	req.Header.Set("Accept", "application/json")
-	req.Header.Set("X-Crisp-Tier", "plugin")
+	req.Header.Set(crispTierHeader, crispTierValue)
 
 	return doProbeRequest(httpClient, req, http.StatusNotFound)
 }