XYZ-37: Advanced Permissions Phase 1 Backend. (#8159)

* XYZ-13: Update Permission and Role structs to new design.

* XYZ-10: Role store.

* XYZ-9/XYZ-44: Roles API endpoints and WebSocket message.

* XYZ-8: Switch server permissions checks to store backed roles.

* XYZ-58: Proper validation of roles where required.

* XYZ-11/XYZ-55: Migration to store backed roles from policy config.

* XYZ-37: Update unit tests to work with database roles.

* XYZ-56: Remove the "guest" role.

* Changes to SetDefaultRolesFromConfig.

* Short-circuit the store if nothing has changed.

* Address first round of review comments.

* Address second round of review comments.

store/store.go

@@ -61,6 +61,7 @@ type Store interface {
 	Status() StatusStore
 	FileInfo() FileInfoStore
 	Reaction() ReactionStore
+	Role() RoleStore
 	Job() JobStore
 	UserAccessToken() UserAccessTokenStore
 	ChannelMemberHistory() ChannelMemberHistoryStore
@@ -461,3 +462,10 @@ type PluginStore interface {
 	Get(pluginId, key string) StoreChannel
 	Delete(pluginId, key string) StoreChannel
 }
+
+type RoleStore interface {
+	Save(role *model.Role) StoreChannel
+	Get(roleId string) StoreChannel
+	GetByName(name string) StoreChannel
+	GetByNames(names []string) StoreChannel
+}