feat: reverse shares (#86)

* add first concept

* add reverse share funcionality to frontend

* allow creator to limit share expiration

* moved reverse share in seperate module

* add table to manage reverse shares

* delete complete share if reverse share was deleted

* optimize function names

* add db migration

* enable reverse share email notifications

* fix config variable descriptions

* fix migration for new installations

backend/src/file/file.module.ts

@@ -1,11 +1,12 @@
 import { Module } from "@nestjs/common";
 import { JwtModule } from "@nestjs/jwt";
+import { ReverseShareModule } from "src/reverseShare/reverseShare.module";
 import { ShareModule } from "src/share/share.module";
 import { FileController } from "./file.controller";
 import { FileService } from "./file.service";
 
 @Module({
-  imports: [JwtModule.register({}), ShareModule],
+  imports: [JwtModule.register({}), ReverseShareModule, ShareModule],
   controllers: [FileController],
   providers: [FileService],
   exports: [FileService],