Update OPA image reference with v1.4.2 (#640)

* Update Dockerfile-opa with v1 release
* Update policy.rego to be compatible with regov1


Signed-off-by: Tyler Schade <tylerschade99@gmail.com>

Author: tjons

ext_authz/Dockerfile-opa

@@ -1,3 +1,3 @@
-FROM openpolicyagent/opa:0.70.0-istio-static@sha256:808342677946849bd359e519666a0b5097885961d2a8f6482e0c99b598e2a996
+FROM openpolicyagent/opa:1.4.2-envoy-1-static@sha256:073bbd180c52f8a148914a577f5030fda007630268a54087796f55cdab2f6732
 
 COPY --chmod=644 ./config/opa-service/policy.rego /etc/policy.rego

ext_authz/config/opa-service/policy.rego

@@ -1,13 +1,14 @@
 package envoy.authz
 
 import input.attributes.request.http as http_request
+import rego.v1
 
-default allow = false
+default allow := false
 
-allow = response {
-  http_request.method == "GET"
-  response := {
-    "allowed": true,
-    "headers": {"x-current-user": "OPA"}
-  }
+allow := response if {
+	http_request.method == "GET"
+	response := {
+		"allowed": true,
+		"headers": {"x-current-user": "OPA"},
+	}
 }