rpc: Add regression tests for encoding/decoding public keys (#15054)

This PR adds some tests to ensure we don't regress in our public key
encoding/decoding capabilities when making changes in this area.

Release Notes:

- N/A

crates/rpc/src/auth.rs

@@ -107,6 +107,20 @@ mod tests {
         assert_eq!(decrypted_token, token);
     }
 
+    #[test]
+    fn test_encode_and_decode_base64_public_key() {
+        // A base64-encoded public key.
+        //
+        // We're using a literal string to ensure that encoding and decoding works across differences in implementations.
+        let encoded_public_key = "MIGJAoGBAMPvufou8wOuUIF1Wlkbtn0ZMM9nC55QJ06nTZvgMfZv5esFVU9-cQO_JC1P9ZoEcMDJweFERnQuQLqzsrMDLFbkdgL128ZU43WOLiQraxaICFIZsPUeTtWMKp2D5bPWsNxs-lnCma7vCAry6fpXuj5AKQdk7cTZJNucgvZQ0uUfAgMBAAE=".to_string();
+
+        // Make sure we can parse the public key.
+        let public_key = PublicKey::try_from(encoded_public_key.clone()).unwrap();
+
+        // Make sure we re-encode to the same format.
+        assert_eq!(encoded_public_key, String::try_from(public_key).unwrap());
+    }
+
     #[test]
     fn test_tokens_are_always_url_safe() {
         for _ in 0..5 {