Enable specifying a secret for flux git creds

Add entrypoints into charts values.yaml for (in order):

• using an existing secret for git credentials
• create git-credentials from user defined username/password
• create git-credentials from user defined privateKey/publicKey/knownHosts

if none of the above are specified, repositories will assume unauthenticated access

chart/templates/argocd/gitrepository.yaml

@@ -10,4 +10,5 @@ spec:
   ref:
     {{- include "validRef" .Values.addons.argocd.git | nindent 4 }}
   {{ include "gitIgnore" . }}
+  {{- include "gitCreds" .Values.git | nindent 2 }}
 {{- end }}