fix: truncate image descriptions (#7699)

* move truncate function to separate file to reuse it

* truncate image descriptions

* show image description limit in UI

* correctly treat null

Co-authored-by: nullobsi <me@nullob.si>

* make truncate Unicode-aware

The strings that truncate returns should now be valid Unicode.

PostgreSQL also counts Unicode Code Points instead of bytes so this
should be correct.

* move truncate to internal, validate in API

Truncating could also be done in src/services/drive/add-file.ts or
src/services/drive/upload-from-url.ts but those would also affect
local images. But local images should result in a hard error if the
image comment is too long.

* avoid overwriting

Co-authored-by: nullobsi <me@nullob.si>

src/server/api/endpoints/drive/files/upload-from-url.ts

@@ -5,6 +5,7 @@ import uploadFromUrl from '@/services/drive/upload-from-url';
 import define from '../../../define';
 import { DriveFiles } from '@/models/index';
 import { publishMainStream } from '@/services/stream';
+import { DB_MAX_IMAGE_COMMENT_LENGTH } from '@/misc/hard-limits';
 
 export const meta = {
 	tags: ['drive'],
@@ -35,7 +36,7 @@ export const meta = {
 		},
 
 		comment: {
-			validator: $.optional.nullable.str,
+			validator: $.optional.nullable.str.max(DB_MAX_IMAGE_COMMENT_LENGTH),
 			default: null,
 		},