feat(flux-system): Add reciever for webhooks

In order to speed up deployments using gitops, this patch adds a webhook
reciever for flux to the mix, that will trigger a repository refresh as
soon as a new commit is pushed to the infrastructure-gitops repository.

clusters/okd4/flux-system/receiver.yaml

+apiVersion: notification.toolkit.fluxcd.io/v1beta1
+kind: Receiver
+metadata:
+  name: gitlab-receiver
+  namespace: flux-system
+spec:
+  events:
+  - Push Hook
+  - Tag Push Hook
+  resources:
+  - kind: GitRepository
+    name: flux-system
+  secretRef:
+    name: gitlab-webhook-token
+  type: gitlab

clusters/okd4/flux-system/webhook-secret.yaml

+apiVersion: v1
+kind: Secret
+metadata:
+    name: gitlab-webhook-token
+    namespace: flux-system
+type: Opaque
+data:
+    token: ENC[AES256_GCM,data:OH3a73YY8Oii3q/gyzllsk2BX8phUMXe8nZNXjUT7CZk6UlWtXY3/c0rAZon3FBDaH1hKDhtsWVVdVcZ07kNOOtlc0ezdHkN5cD/fEfdPR8U+XttLsr+DQ==,iv:2wqK2ufJTV5MdRmDBKx+f+PxVGwoNox/MTJk4RXIml8=,tag:y/fvRyAYXdPKOCjBOsx3BA==,type:str]
+sops:
+    kms: []
+    gcp_kms: []
+    azure_kv: []
+    hc_vault: []
+    age: []
+    lastmodified: "2021-08-13T22:24:25Z"
+    mac: ENC[AES256_GCM,data:wbKWI4Qdjg8FYA56ASgchwZWT+yi6HT9ix1kwpH6wQ8hkVLTvNa2/tPQCILGcG/6DWGWtgQbKLp8wqp15MpRy5t/FqH2xTBXr6dY/5iDbvAgUA17QQI1w6xFIJoxdanthGFtrlZZTPz8YC9bAXpCN3Y1Icj4ZWgkzeqrn/QPd8Q=,iv:pm29MkED8RzetecXrrAOJtRQZmolKCLW1L5tF2hB+F0=,tag:VQym4XS8vbzWTaxydHYKJg==,type:str]
+    pgp:
+        - created_at: "2021-08-13T22:23:22Z"
+          enc: |
+            -----BEGIN PGP MESSAGE-----
+
+            hQIMA1u//sli4/n1ARAAyPUuDlqcn8uoyARE0anQfduu8UdylmAUBixoc7HqZy8t
+            E8psRdURyyMrqCinFQKiJIYaK5BAB80WNx5dw0tYz6HRmiojQVtyxcwle8edtiZO
+            jnw22USDiIfqNrYQd1lxE4pFKLKOwq897oXiLcwK4tdItCrlFWrklNetDZhEEfdB
+            /1Oz28lnHBsxmQyxYu8gsgQ2MekYMek1FTBP9ht/xWFH1GoASU27jeOxtUPre9QT
+            3Wf9NmgCPf0BW09S3DprUdjcphZ0qLp8xYkZ8FNyVWXAJ+EjoTO/AXbsNqAN8BF+
+            G8HGbV9QtXAUDT8zhF8nf7BVeKdTc5jhPaFlXOc9UwzdZfAuFwOw4Js34uIHC2lz
+            nVrn9qKlfsr3D9ab7Q7OoRnftXpbsnthCV5kkHWdnb5JbMkVxep001TVSbJoh97P
+            aTR4xCOcHvrDx9LR7ydXX0vMzki2k7zzJvcDtn9GwGAljz2M8epAi4BxEIPjyY52
+            yQMEErjFBUs48flB8sL/JIuBlxX5DlxekNuXBdTaoeYTN+AKgXEaH02FPgL8K3SY
+            mkc9bDEtTGo6PLpVaF/8qk1BRaoQ4yOrjASqrlzzbb8oZywSu39JvvwBesyBsXUs
+            RtRbop9hb5MYJ51010FBRMXuqbr2j9C4vMGgv4HtpOpKm0rmDFIB2uUoqfg6Pe7S
+            XgFd+cr4u3bHPsPnOgYxqhfG6aIj4cJyFmiBSH1yjcFUYBW+5i4pMeMYB+RQ/W2+
+            hfPYxkboXoZXwJbJYMhwh56UvaH8jcV1idzthoRNPngHG3WbYNwVarGHRScwhyU=
+            =tTg4
+            -----END PGP MESSAGE-----
+          fp: 9D02A9AD73EF7F3D5F657AC2B392F6EB325E8C50
+        - created_at: "2021-08-13T22:23:22Z"
+          enc: |-
+            -----BEGIN PGP MESSAGE-----
+
+            wcFMA7kpg2bgzVHcARAAjUgfdKLRkCovt4OvijlWqmOwemHvD5btBERoGvAR0Icu
+            xHcvUGdPtoMQ0JsZ71HT5Bt2efcmrYbBsUPSbXbbrWzqCx+JvO93oeBxY3AaVbzz
+            NmHOBY/VyTyzxIOxtW/Ob7VDAuDD4bv0NhtHJBcyqh9gdNXtZxTCbnyXvk6rbH7Q
+            k9HIw/A68QfR5rHppHmByBzc5OfuEvcGBInZgUUATUvYkEn2TfB4LLZ++L0jX8C6
+            2lqqURTOTZ2TVq8qijUXa+hNt4kYpHojySyUeNWTwCgAxAeMw++DGKciA5WzKTAY
+            bLALBcYMAh8lydJ//ISi3pyMvVsCjlN3BpM4VA/+0v5fkEtFd7GDMhuB1/CYza9n
+            YTo0tE9mZapoDmlIs6q7mDiD7xs4iNBeGpTU3vcDgImFZjNzHFWddN8s3ujzPZlD
+            7tDCcXh7mPFlWq0EUSy7DWbgbj945OuEKEplV/h0lVf93D67KpJEkaH/TnnYjXCQ
+            t51r+wAg8naC9Dfj3QHZt9xrmk3j3uMQBM6rzGMRvXqdwjSOH1uqULxTTVZzJryP
+            2LftqLxZrD5zdG8Gs0lYe+iwmHVhIOOfY1weLN3Y4yKbhk8aHUKFxhoTN/bPDBgk
+            sLBL4uqNSL1tku/ShZ+UOK1Rh82Q0wpUit+8OXi5biNGwkcEIwhpPpfm8yorL4bS
+            5gFWiuXXESNKa0ArSBrrLp5bncIMfIQ7wGohlKMVSf7NRzDFk49u+KC/10NBFaVP
+            0yRB+wxhQBMr8fxVAJsThqTkJr6FK6FD70/La76QSdJlmuJS19f5AA==
+            =l6ls
+            -----END PGP MESSAGE-----
+          fp: 286791FB6648539775DB31B8FCB98C2A3EC6F601
+    encrypted_regex: ^(data|stringData)$
+    version: 3.7.1