Add support for global image prefix

This change adds an imagePrefix attribute to enable using
custom images for all the service at once using a single attribute
which default to "docker.io/zuul".

Change-Id: Ia1a5dd4aa9de410937f59a769019dcdb34167944

conf/zuul/input.dhall

@@ -142,6 +142,7 @@ let Schemas =
 let Input =
       { Type =
           { name : Text
+          , imagePrefix : Optional Text
           , merger : Schemas.Merger.Type
           , executor : Schemas.Executor.Type
           , web : Schemas.Web.Type
@@ -157,7 +158,8 @@ let Input =
           , withCertManager : Bool
           }
       , default =
-          { database = None UserSecret
+          { imagePrefix = None Text
+          , database = None UserSecret
           , zookeeper = None UserSecret
           , externalConfig = Schemas.ExternalConfigs.default
           , merger = Schemas.Merger.default

conf/zuul/resources.dhall

@@ -142,7 +142,10 @@ in      \(input : Input)
                       }
                     ]
 
-        let org = "docker.io/zuul"
+        let org =
+              merge
+                { None = "docker.io/zuul", Some = \(prefix : Text) -> prefix }
+                input.imagePrefix
 
         let version = "latest"
 

deploy/crds/zuul-ci_v1alpha1_zuul_cr.yaml

@@ -3,6 +3,7 @@ kind: Zuul
 metadata:
   name: zuul
 spec:
+  imagePrefix: docker.io/zuul
   executor:
     count: 1
     ssh_key: