Add import protocol (#1558)

Adds a protocol for repository imports (either from an URL, a dump file or a SCM-Manager repository archive).
This protocol documents single steps of an import, the time and the user and is accessible via a dedicated REST
endpoint or a simple ui.

The id of the log is added to the repository imported event, so that plugins like the landingpage or mail can link to these logs.

scm-ui/ui-api/src/index.ts

@@ -43,6 +43,7 @@ export * from "./plugins";
 export * from "./repository-roles";
 export * from "./permissions";
 export * from "./sources";
+export * from "./import";
 
 export { default as ApiProvider } from "./ApiProvider";
 export * from "./ApiProvider";