Restore url.PathEscape on user-supplied path segments in url.JoinPath calls

url.JoinPath does not percent-encode slashes or reserved characters in
its arguments, so user-supplied values (group IDs, slugs, team IDs) must
be wrapped with url.PathEscape to prevent path traversal. Update cursor
rule and contrib guide to codify this as a mandatory practice.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/accessreview/drivers/clickup.go

@@ -71,7 +71,7 @@ type clickupTeamResponse struct {
 }
 
 func (d *ClickUpDriver) ListAccounts(ctx context.Context) ([]AccountRecord, error) {
-	endpoint, err := url.JoinPath("https://api.clickup.com", "api", "v2", "team", d.teamID)
+	endpoint, err := url.JoinPath("https://api.clickup.com", "api", "v2", "team", url.PathEscape(d.teamID))
 	if err != nil {
 		return nil, fmt.Errorf("cannot build clickup team URL: %w", err)
 	}