Enable sending an email to users not found in the Google Workspace di…

…rectory (#666)

internal/api/v2/me.go

@@ -88,6 +88,37 @@ func MeHandler(srv server.Server) http.Handler {
 					nil,
 					"user_email", userEmail,
 				)
+
+				// If configured, send an email to the user to notify them that their
+				// account was not found in the directory.
+				if srv.Config.Email != nil && srv.Config.Email.Enabled &&
+					srv.Config.GoogleWorkspace != nil &&
+					srv.Config.GoogleWorkspace.UserNotFoundEmail != nil &&
+					srv.Config.GoogleWorkspace.UserNotFoundEmail.Enabled &&
+					srv.Config.GoogleWorkspace.UserNotFoundEmail.Body != "" &&
+					srv.Config.GoogleWorkspace.UserNotFoundEmail.Subject != "" {
+					_, err = srv.GWService.SendEmail(
+						[]string{userEmail},
+						srv.Config.Email.FromAddress,
+						srv.Config.GoogleWorkspace.UserNotFoundEmail.Subject,
+						srv.Config.GoogleWorkspace.UserNotFoundEmail.Body,
+					)
+					if err != nil {
+						srv.Logger.Error("error sending user not found email",
+							"error", err,
+							"method", r.Method,
+							"path", r.URL.Path,
+							"user_email", userEmail,
+						)
+					} else {
+						srv.Logger.Info("user not found email sent",
+							"method", r.Method,
+							"path", r.URL.Path,
+							"user_email", userEmail,
+						)
+					}
+				}
+
 				return
 			}
 			p := ppl[0]

internal/config/config.go

@@ -232,6 +232,10 @@ type GoogleWorkspace struct {
 	// create_docs_as_user is true in the auth block, so document notification
 	// settings will be the same as when a user creates their own document.
 	TemporaryDraftsFolder string `hcl:"temporary_drafts_folder,optional"`
+
+	// UserNotFoundEmail is the configuration to send an email when a user is not
+	// found in Google Workspace.
+	UserNotFoundEmail *GoogleWorkspaceUserNotFoundEmail `hcl:"user_not_found_email,block"`
 }
 
 // GoogleWorkspaceOAuth2 is the configuration to use OAuth 2.0 to access Google
@@ -249,6 +253,20 @@ type GoogleWorkspaceOAuth2 struct {
 	RedirectURI string `hcl:"redirect_uri,optional"`
 }
 
+// GoogleWorkspaceUserNotFoundEmail is the configuration to send an email when a
+// user is not found in Google Workspace.
+type GoogleWorkspaceUserNotFoundEmail struct {
+	// Body is the body of the email.
+	Body string `hcl:"body,optional"`
+
+	// Enabled enables sending an email when a user is not found in Google
+	// Workspace.
+	Enabled bool `hcl:"enabled,optional"`
+
+	// Subject is the subject of the email.
+	Subject string `hcl:"subject,optional"`
+}
+
 // Jira is the configuration for Hermes to work with Jira.
 type Jira struct {
 	// APIToken is the API token for authenticating to Jira.