fix: Correct JSON format for SecurityScheme and Security in test data

Fixed AgentCard JSON test payload to use proper protobuf JSON format:
- Changed SecurityScheme from flat `{"scheme": "openIdConnect", ...}` to oneof wrapper format `{"openIdConnectSecurityScheme": {...}}`
- Changed Security from flat `{"google": [...]}` to proper structure `{"schemes": {"google": {"list": [...]}}}`

This aligns with the protobuf message definitions where SecurityScheme uses a oneof field and Security uses a map<string, StringList>.

Fixes A2ACardResolverTest failures.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: ehsavoie

http-client/src/test/java/io/a2a/client/http/JsonMessages.java

@@ -30,11 +30,12 @@ public class JsonMessages {
                  },
                  "securitySchemes": {
                    "google": {
-                     "type": "openIdConnect",
-                     "openIdConnectUrl": "https://accounts.google.com/.well-known/openid-configuration"
+                     "openIdConnectSecurityScheme": {
+                       "openIdConnectUrl": "https://accounts.google.com/.well-known/openid-configuration"
+                     }
                    }
                  },
-                 "security": [{ "google": ["openid", "profile", "email"] }],
+                 "security": [{ "schemes": { "google": { "list": ["openid", "profile", "email"] } } }],
                  "defaultInputModes": ["application/json", "text/plain"],
                  "defaultOutputModes": ["application/json", "image/png"],
                  "skills": [
@@ -102,11 +103,12 @@ public class JsonMessages {
                 },
                 "securitySchemes": {
                   "google": {
-                    "type": "openIdConnect",
-                    "openIdConnectUrl": "https://accounts.google.com/.well-known/openid-configuration"
+                    "openIdConnectSecurityScheme": {
+                      "openIdConnectUrl": "https://accounts.google.com/.well-known/openid-configuration"
+                    }
                   }
                 },
-                "security": [{ "google": ["openid", "profile", "email"] }],
+                "security": [{ "schemes": { "google": { "list": ["openid", "profile", "email"] } } }],
                 "defaultInputModes": ["application/json", "text/plain"],
                 "defaultOutputModes": ["application/json", "image/png"],
                 "skills": [