feat: configurable images for istio-gateway (#323)

# Description
More details in: #322

# Summary of changes:
- Added proxy-image config option.
- Updated manifest template with placeholder for proxy image.
- Modified charm code to render manifest with proxy image from configuration.

# Testing

For complete testing refer to #322
---------

Co-authored-by: Orfeas Kourkakis <[email protected]>

charms/istio-gateway/config.yaml

@@ -8,3 +8,7 @@ options:
     type: string
     description: |
       Type of service for the ingress gateway out of: 'ClusterIP', 'LoadBalancer', or 'NodePort'.
+  proxy-image:
+    default: 'docker.io/istio/proxyv2:1.17.3'
+    description: Istio Proxy image
+    type: string

charms/istio-gateway/src/charm.py

@@ -69,6 +69,7 @@ def start(self, event):
         rendered = template.render(
             kind=self.model.config["kind"],
             namespace=self.model.name,
+            proxy_image=self.model.config["proxy-image"],
             pilot_host=pilot["service-name"],
             pilot_port=pilot["service-port"],
             gateway_service_type=self.model.config["gateway_service_type"],
@@ -88,6 +89,7 @@ def remove(self, event):
         rendered = template.render(
             kind=self.model.config["kind"],
             namespace=self.model.name,
+            proxy_image=self.model.config["proxy-image"],
             pilot_host="foo",
             pilot_port="foo",
         )

charms/istio-gateway/src/manifest.yaml

@@ -116,7 +116,7 @@ spec:
               value: standard
             - name: ISTIO_META_CLUSTER_ID
               value: Kubernetes
-          image: docker.io/istio/proxyv2:1.17.3
+          image: {{ proxy_image }}
           name: istio-proxy
           ports:
             - containerPort: 15021