Refactor Policy Enforcer to Policy Checker

- Renamed the `PolicyEnforcer` interface and related implementations to `PolicyChecker` for clarity and consistency.
- Updated configuration keys in YAML files to reflect the new `checkPolicy` terminology.
- Adjusted related code, tests, and documentation to support the new naming convention and ensure compatibility.
- Enhanced comments and examples for the `checkPolicy` configuration to improve usability.

config/local-simple.yaml

@@ -66,10 +66,13 @@ modules:
           id: router
           config:
             routingConfig: ./config/local-simple-routing.yaml
-        policyEnforcer:
-          id: policyenforcer
+        checkPolicy:
+          id: opapolicychecker
           config:
-            policyPaths: "./policies"
+            type: file
+            location: ./pkg/plugin/implementation/opapolicychecker/testdata/example.rego
+            query: "data.policy.result"
+            refreshIntervalSeconds: "300"
         middleware:
           - id: reqpreprocessor
             config:
@@ -77,7 +80,7 @@ modules:
               role: bap
       steps:
         - validateSign
-        - policyEnforcer
+        - checkPolicy
         - addRoute
   
   - name: bapTxnCaller
@@ -167,13 +170,16 @@ modules:
           id: router
           config:
             routingConfig: ./config/local-simple-routing-BPPReceiver.yaml
-        policyEnforcer:
-          id: policyenforcer
+        checkPolicy:
+          id: opapolicychecker
           config:
-            policyPaths: "./policies"
+            type: file
+            location: ./pkg/plugin/implementation/opapolicychecker/testdata/example.rego
+            query: "data.policy.result"
+            refreshIntervalSeconds: "300"
       steps:
         - validateSign
-        - policyEnforcer
+        - checkPolicy
         - addRoute
   
   - name: bppTxnCaller