Fixes https://github.com/turt2live/matrix-media-repo/issues/457

For https://github.com/turt2live/matrix-media-repo/issues/457

The download pipeline returns a CancelCloser, making this required.

For https://github.com/turt2live/matrix-media-repo/issues/457

For https://github.com/turt2live/matrix-media-repo/issues/457

For https://github.com/turt2live/matrix-media-repo/issues/457

Fixes https://github.com/turt2live/matrix-media-repo/issues/447

Fixes https://github.com/turt2live/matrix-media-repo/issues/446

We instead just generate something unique enough.

This is what their documentation recommends, even if weird.

This was causing large allocations in heap: https://github.com/turt2live/matrix-media-repo/issues/445

See https://github.com/matrix-org/matrix-spec-proposals/pull/2448/files#r1316159044

This reverts commit 9ee13765.

This reverts commit 9d4c97f4.

Fixes https://github.com/turt2live/matrix-media-repo/issues/428

Fixes https://github.com/turt2live/matrix-media-repo/issues/425

See https://github.com/turt2live/matrix-media-repo/issues/445

Fixes https://github.com/turt2live/matrix-media-repo/issues/451

Fixes https://github.com/turt2live/matrix-media-repo/issues/440

This reverts commit d3eb5a99.

This reverts commit 4adff75b.

This reverts commit 1ae78235.

For https://github.com/turt2live/matrix-media-repo/issues/445