feat(extensions): introduce extension support (#2527)

* wip

* wip: missing repository & tags removal

* feat(registry): private registry management

* style(plugin-details): update view

* wip

* wip

* wip

* feat(plugins): add license info

* feat(plugins): browse feature preview

* feat(registry-configure): add the ability to configure registry management

* style(app): update text in app

* feat(plugins): add plugin version number

* feat(plugins): wip plugin upgrade process

* feat(plugins): wip plugin upgrade

* feat(plugins): add the ability to update a plugin

* feat(plugins): init plugins at startup time

* feat(plugins): add the ability to remove a plugin

* feat(plugins): update to latest plugin definitions

* feat(plugins): introduce plugin-tooltip component

* refactor(app): relocate plugin files to app/plugins

* feat(plugins): introduce PluginDefinitionsURL constant

* feat(plugins): update the flags used by the plugins

* feat(plugins): wip

* feat(plugins): display a label when a plugin has expired

* wip

* feat(registry-creation): update registry creation logic

* refactor(registry-creation): change name/ids for inputs

* feat(api): pass registry type to management configuration

* feat(api): unstrip /v2 in regsitry proxy

* docs(api): add TODO

* feat(store): mockup-1

* feat(store): mockup 2

* feat(store): mockup 2

* feat(store): update mockup-2

* feat(app): add unauthenticated event check

* update gruntfile

* style(support): update support views

* style(support): update product views

* refactor(extensions): refactor plugins to extensions

* feat(extensions): add a deal property

* feat(extensions): introduce ExtensionManager

* style(extensions): update extension details style

* feat(extensions): display license/company when enabling extension

* feat(extensions): update extensions views

* feat(extensions): use ProductId defined in extension schema

* style(app): remove padding left for form section title elements

* style(support): use per host model

* refactor(extensions): multiple refactors related to extensions mecanism

* feat(extensions): update tls file path for registry extension

* feat(extensions): update registry management configuration

* feat(extensions): send license in header to extension proxy

* fix(proxy): fix invalid default loopback address

* feat(extensions): add header X-RegistryManagement-ForceNew for specific operations

* feat(extensions): add the ability to display screenshots

* feat(extensions): center screenshots

* style(extensions): tune style

* feat(extensions-details): open full screen image on click (#2517)

* feat(extension-details): show magnifying glass on images

* feat(extensions): support extension logo

* feat(extensions): update support logos

* refactor(lint): fix lint issues

api/http/handler/registries/proxy.go

@@ -0,0 +1,78 @@
+package registries
+
+import (
+	"encoding/json"
+	"net/http"
+	"strconv"
+
+	httperror "github.com/portainer/libhttp/error"
+	"github.com/portainer/libhttp/request"
+	"github.com/portainer/portainer"
+)
+
+// request on /api/registries/:id/v2
+func (handler *Handler) proxyRequestsToRegistryAPI(w http.ResponseWriter, r *http.Request) *httperror.HandlerError {
+	registryID, err := request.RetrieveNumericRouteVariableValue(r, "id")
+	if err != nil {
+		return &httperror.HandlerError{http.StatusBadRequest, "Invalid registry identifier route variable", err}
+	}
+
+	registry, err := handler.RegistryService.Registry(portainer.RegistryID(registryID))
+	if err == portainer.ErrObjectNotFound {
+		return &httperror.HandlerError{http.StatusNotFound, "Unable to find a registry with the specified identifier inside the database", err}
+	} else if err != nil {
+		return &httperror.HandlerError{http.StatusInternalServerError, "Unable to find a registry with the specified identifier inside the database", err}
+	}
+
+	extension, err := handler.ExtensionService.Extension(portainer.RegistryManagementExtension)
+	if err == portainer.ErrObjectNotFound {
+		return &httperror.HandlerError{http.StatusNotFound, "Registry management extension is not enabled", err}
+	} else if err != nil {
+		return &httperror.HandlerError{http.StatusInternalServerError, "Unable to find a extension with the specified identifier inside the database", err}
+	}
+
+	var proxy http.Handler
+	proxy = handler.ProxyManager.GetExtensionProxy(portainer.RegistryManagementExtension)
+	if proxy == nil {
+		proxy, err = handler.ProxyManager.CreateExtensionProxy(portainer.RegistryManagementExtension)
+		if err != nil {
+			return &httperror.HandlerError{http.StatusInternalServerError, "Unable to register registry proxy", err}
+		}
+	}
+
+	managementConfiguration := registry.ManagementConfiguration
+	if managementConfiguration == nil {
+		managementConfiguration = createDefaultManagementConfiguration(registry)
+	}
+
+	encodedConfiguration, err := json.Marshal(managementConfiguration)
+	if err != nil {
+		return &httperror.HandlerError{http.StatusInternalServerError, "Unable to encode management configuration", err}
+	}
+
+	id := strconv.Itoa(int(registryID))
+	r.Header.Set("X-RegistryManagement-Key", id)
+	r.Header.Set("X-RegistryManagement-URI", registry.URL)
+	r.Header.Set("X-RegistryManagement-Config", string(encodedConfiguration))
+	r.Header.Set("X-PortainerExtension-License", extension.License.LicenseKey)
+
+	http.StripPrefix("/registries/"+id, proxy).ServeHTTP(w, r)
+	return nil
+}
+
+func createDefaultManagementConfiguration(registry *portainer.Registry) *portainer.RegistryManagementConfiguration {
+	config := &portainer.RegistryManagementConfiguration{
+		Type: registry.Type,
+		TLSConfig: portainer.TLSConfiguration{
+			TLS: false,
+		},
+	}
+
+	if registry.Authentication {
+		config.Authentication = true
+		config.Username = registry.Username
+		config.Password = registry.Password
+	}
+
+	return config
+}