Adding ImagePullPolicy config option to OSM Charms

Change-Id: I04ad8444088e8a360755dc4e22b7ea53942682b2
Signed-off-by: sousaedu <eduardo.sousa@canonical.com>
diff --git a/installers/charm/ng-ui/src/charm.py b/installers/charm/ng-ui/src/charm.py
index 5388466..cf0b091 100755
--- a/installers/charm/ng-ui/src/charm.py
+++ b/installers/charm/ng-ui/src/charm.py
@@ -54,6 +54,7 @@
     ingress_class: Optional[str]
     ingress_whitelist_source_range: Optional[str]
     tls_secret_name: Optional[str]
+    image_pull_policy: Optional[str]
 
     @validator("port")
     def validate_port(cls, v):
@@ -81,6 +82,18 @@
             ip_network(v)
         return v
 
+    @validator("image_pull_policy")
+    def validate_image_pull_policy(cls, v):
+        values = {
+            "always": "Always",
+            "ifnotpresent": "IfNotPresent",
+            "never": "Never",
+        }
+        v = v.lower()
+        if v not in values.keys():
+            raise ValueError("value must be always, ifnotpresent or never")
+        return values[v]
+
 
 class NgUiCharm(CharmedOsmBase):
     def __init__(self, *args) -> NoReturn:
@@ -121,7 +134,9 @@
         # Create Builder for the PodSpec
         pod_spec_builder = PodSpecV3Builder()
         # Build Container
-        container_builder = ContainerV3Builder(self.app.name, image_info)
+        container_builder = ContainerV3Builder(
+            self.app.name, image_info, config.image_pull_policy
+        )
         container_builder.add_port(name=self.app.name, port=config.port)
         container = container_builder.build()
         container_builder.add_tcpsocket_readiness_probe(