change: use RFC 9535 syntax for jwt-role-claim-key config

BREAKING CHANGE

Breaks the string comparison operators implemented in #3813. Those can
be replaced with regex searches using JSON Path `search()` function.

Signed-off-by: Taimoor Zaeem <taimoorzaeem@gmail.com>

test/io/configs/expected/no-defaults-with-db.config

@@ -29,7 +29,7 @@ db-tx-end = "commit-allow-override"
 db-uri = "postgresql://"
 jwt-aud = "https://example.org"
 jwt-cache-max-entries = 86400
-jwt-role-claim-key = ".\"a\".\"role\""
+jwt-role-claim-key = "$$.a.role"
 jwt-secret = "OVERRIDE=REALLY=REALLY=REALLY=REALLY=VERY=SAFE"
 jwt-secret-is-base64 = false
 log-level = "info"