Add SPA UI for GARM

This change adds a single page application front-end to GARM. It uses
a generated REST client, built from the swagger definitions, the websocket
interface for live updates of entities and eager loading of everything
except runners, as users may have many runners and we don't want to load
hundreds of runners in memory.

Proper pagination should be implemented in the API, in future commits,
to avoid loading lots of elements for no reason.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

config/config.go

@@ -663,6 +663,21 @@ func (m *Metrics) Duration() time.Duration {
 	return duration
 }
 
+// WebUI holds configuration for the web UI
+type WebUI struct {
+	EnableWebUI bool `toml:"enable" json:"enable"`
+}
+
+// Validate validates the WebUI config
+func (w *WebUI) Validate() error {
+	return nil
+}
+
+// GetWebappPath returns the webapp path with proper formatting
+func (w *WebUI) GetWebappPath() string {
+	return "/ui/"
+}
+
 // APIServer holds configuration for the API server
 // worker
 type APIServer struct {
@@ -671,6 +686,7 @@ type APIServer struct {
 	UseTLS      bool      `toml:"use_tls" json:"use-tls"`
 	TLSConfig   TLSConfig `toml:"tls" json:"tls"`
 	CORSOrigins []string  `toml:"cors_origins" json:"cors-origins"`
+	WebUI       WebUI     `toml:"webui" json:"webui"`
 }
 
 // BindAddress returns a host:port string.
@@ -696,6 +712,11 @@ func (a *APIServer) Validate() error {
 		// when we try to bind to it.
 		return fmt.Errorf("invalid IP address")
 	}
+
+	if err := a.WebUI.Validate(); err != nil {
+		return fmt.Errorf("invalid webui config: %w", err)
+	}
+
 	return nil
 }