Downgrade validator crate to 0.15.0

Fresh build with 0.16 was hitting lifetime issues deep in Validator source code.
It looks like validator git history may have been altered as public git history
doesn't match downloaded code. It also looks like references to 0.16 release are
missing / yanked from various docs pages so perhaps there were other known issues.
Upgrading to validator > 0.17 requires breaking changes so simplest fix for now is
to downgrade to 0.15 release.

Author: sd109

Cargo.lock

@@ -70,7 +70,7 @@ tracing-opentelemetry = "0.21"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 url = { version = "2", features = ["serde"] }
 uuid = { version = "1.12.1", features = ["v4"] }
-validator = { version = "0.16", features = ["derive"] }
+validator = { version = "0.15", features = ["derive"] }
 zerocopy = { version = "0.6.1", features = ["alloc", "simd"] }
 zune-inflate = "0.2.54"