Deprecation warnings for Rbnacl backed functionality

Author: anakinj

CHANGELOG.md

@@ -18,6 +18,7 @@
 - Improved documentation for public apis [#629](https://github.com/jwt/ruby-jwt/pull/629) ([@anakinj](https://github.com/anakinj))
 - Use correct methods when raising error during signing/verification with EdDSA [#633](https://github.com/jwt/ruby-jwt/pull/633)
 - Fix JWT::EncodedToken behavior with empty string as token [#640](https://github.com/jwt/ruby-jwt/pull/640) ([@ragalie](https://github.com/ragalie))
+- Deprecation warnings for rbnacl backed functionality [#641](https://github.com/jwt/ruby-jwt/pull/641) ([@anakinj](https://github.com/anakinj))
 - Your contribution here
 
 ## [v2.9.3](https://github.com/jwt/ruby-jwt/tree/v2.9.3) (2024-10-03)

lib/jwt/jwa/eddsa.rb

@@ -13,12 +13,16 @@ def initialize(alg)
       def sign(data:, signing_key:)
         raise_sign_error!("Key given is a #{signing_key.class} but has to be an RbNaCl::Signatures::Ed25519::SigningKey") unless signing_key.is_a?(RbNaCl::Signatures::Ed25519::SigningKey)
 
+        Deprecations.warning('Using Ed25519 keys is deprecated and will be removed in a future version of ruby-jwt. Please use the ruby-eddsa gem instead.')
+
         signing_key.sign(data)
       end
 
       def verify(data:, signature:, verification_key:)
         raise_verify_error!("key given is a #{verification_key.class} but has to be a RbNaCl::Signatures::Ed25519::VerifyKey") unless verification_key.is_a?(RbNaCl::Signatures::Ed25519::VerifyKey)
 
+        Deprecations.warning('Using Ed25519 keys is deprecated and will be removed in a future version of ruby-jwt. Please use the ruby-eddsa gem instead.')
+
         verification_key.verify(signature, data)
       rescue RbNaCl::CryptoError
         false

lib/jwt/jwk/okp_rbnacl.rb

@@ -11,7 +11,7 @@ class OKPRbNaCl < KeyBase
 
       def initialize(key, params = nil, options = {})
         params ||= {}
-
+        Deprecations.warning('Using the OKP JWK for Ed25519 keys is deprecated and will be removed in a future version of ruby-jwt. Please use the ruby-eddsa gem instead.')
         # For backwards compatibility when kid was a String
         params = { kid: params } if params.is_a?(String)