Feature/infrastructure roles (#91)

* Add infrastructure roles configured globally.

Those are the roles defined in the operator itself. The operator's
configuration refers to the secret containing role names, passwords
and membership information. While they are referred to as roles, in
reality those are users.

In addition, improve the regex to filter out invalid users and
make sure user secret names are compatible with DNS name spec.

Add an example manifest for the infrastructure roles.

pkg/spec/postgresql.go

@@ -79,7 +79,7 @@ type PostgresSpec struct {
 	NumberOfInstances   int32                `json:"numberOfInstances"`
 	Users               map[string]UserFlags `json:"users"`
 	MaintenanceWindows  []MaintenanceWindow  `json:"maintenanceWindows,omitempty"`
- 	ClusterName         string				 `json:"-"`
+	ClusterName         string               `json:"-"`
 }
 
 type PostgresqlList struct {
@@ -193,7 +193,7 @@ type PostgresqlCopy Postgresql
 
 func clusterName(clusterName string, teamName string) (string, error) {
 	teamNameLen := len(teamName)
-	if len(clusterName) < teamNameLen + 2 {
+	if len(clusterName) < teamNameLen+2 {
 		return "", fmt.Errorf("Name is too short")
 	}
 	if strings.ToLower(clusterName[:teamNameLen]) != strings.ToLower(teamName) {

pkg/spec/types.go

@@ -37,4 +37,5 @@ type PgUser struct {
 	Name     string
 	Password string
 	Flags    []string
+	MemberOf string
 }