Enforce explicit function return types

This re-enables the `@typescript-eslint/explicit-module-boundary-types`
check and also enables the
`@typescript-eslint/explicit-function-return-type` check.

Signed-off-by: David Mehren <git@herrmehren.de>

src/api/private/tokens/tokens.controller.ts

@@ -53,7 +53,7 @@ export class TokensController {
 
   @Delete('/:keyId')
   @HttpCode(204)
-  async deleteToken(@Param('keyId') keyId: string) {
+  async deleteToken(@Param('keyId') keyId: string): Promise<void> {
     return await this.authService.removeToken(keyId);
   }
 }

src/api/public/me/me.controller.ts

@@ -86,7 +86,10 @@ export class MeController {
   @UseGuards(TokenAuthGuard)
   @Delete('history/:note')
   @HttpCode(204)
-  deleteHistoryEntry(@Req() req: Request, @Param('note') note: string) {
+  deleteHistoryEntry(
+    @Req() req: Request,
+    @Param('note') note: string,
+  ): Promise<void> {
     // ToDo: Check if user is allowed to delete note
     try {
       return this.historyService.deleteHistoryEntry(note, req.user);

src/api/public/monitoring/monitoring.controller.ts

@@ -25,7 +25,7 @@ export class MonitoringController {
 
   @UseGuards(TokenAuthGuard)
   @Get('prometheus')
-  getPrometheusStatus() {
+  getPrometheusStatus(): string {
     return '';
   }
 }

src/api/utils/markdownbody-decorator.ts

@@ -41,7 +41,7 @@ export const MarkdownBody = createParamDecorator(
     }
   },
   [
-    (target, key) => {
+    (target, key): void => {
       ApiConsumes('text/markdown')(
         target,
         key,