Allow preferred_username claim to be set for Crowd connector (#1684)

* Add atlassiancrowd connector to list in readme

* Add TestIdentityFromCrowdUser

* Set preferred_username claim when configured

* Add preferredUsernameField option to docs

* Log warning when mapping invalid crowd field

connector/atlassiancrowd/atlassiancrowd.go

@@ -35,6 +35,7 @@ import (
 //       - admin
 //       # Prompt for username field
 //       usernamePrompt: Login
+//		 preferredUsernameField: name
 //
 type Config struct {
 	BaseURL      string   `json:"baseURL"`
@@ -42,6 +43,11 @@ type Config struct {
 	ClientSecret string   `json:"clientSecret"`
 	Groups       []string `json:"groups"`
 
+	// PreferredUsernameField allows users to set the field to any of the
+	// following values: "key", "name" or "email".
+	// If unset, the preferred_username field will remain empty.
+	PreferredUsernameField string `json:"preferredUsernameField"`
+
 	// UsernamePrompt allows users to override the username attribute (displayed
 	// in the username/password prompt). If unset, the handler will use.
 	// "Username".
@@ -368,6 +374,19 @@ func (c *crowdConnector) identityFromCrowdUser(user crowdUser) (connector.Identi
 		EmailVerified: true,
 	}
 
+	switch c.PreferredUsernameField {
+	case "key":
+		identity.PreferredUsername = user.Key
+	case "name":
+		identity.PreferredUsername = user.Name
+	case "email":
+		identity.PreferredUsername = user.Email
+	default:
+		if c.PreferredUsernameField != "" {
+			c.logger.Warnf("preferred_username left empty. Invalid crowd field mapped to preferred_username: %s", c.PreferredUsernameField)
+		}
+	}
+
 	return identity, nil
 }