more use of identifiable errors, improvements to inner error rendering, and more heuristics for is-retryable-error

packages/backend/src/server/api/endpoints/gallery/posts/create.ts

@@ -72,7 +72,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 			))).filter(x => x != null);
 
 			if (files.length === 0) {
-				throw new Error();
+				throw new Error('no files specified');
 			}
 
 			const post = await this.galleryPostsRepository.insertOne(new MiGalleryPost({

packages/backend/src/server/api/endpoints/gallery/posts/update.ts

@@ -73,7 +73,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				))).filter(x => x != null);
 
 				if (files.length === 0) {
-					throw new Error();
+					throw new Error('no files');
 				}
 			}