Signed upload URL for existing files in blob storage

[IzStriker]

Discussed in https://github.com/orgs/supabase/discussions/14538

^{Originally posted by IzStriker May 23, 2023} Hi.

I noticed it isn't possible to create a signed upload URL for existing objects in blob storage. Yet it seems that the storage-js library has the functionality to upsert files via a signed upload URL. Was there a specific reason the decision was made for this restriction, technical or otherwise? If not I would be more than happy to contribute to resolve this.

Generating signed upload URL for existing object error: https://github.com/supabase/storage-api/blob/81e9b7b6ed762f2f21bce9f39dd3b4cf7ce38a7a/src/storage/object.ts#LL534C3-L537C1

Upseritng file via supabase storage js client: https://github.com/supabase/storage-js/blob/b2e3486222126620cc65a5a1c1f967d25b4fb099/src/packages/StorageFileApi.ts#LL83C3-L85C8