cloudflare/miniflare v2.12.1 on GitHub

Bump undici to 5.20.0, addressing GHSA-5r9g-qh6m-jxff and GHSA-r6ch-mqf9-qc9w. Thanks @WalshyDev and @Cherry for the PR.
Ensure global uniqueness of Durable Objects across mounts. Previously, it was possible to have multiple Durable Object instances with the same ID if they were created from different mounts. Closes #461, thanks @Finistere.
Return a R2MultipartUpload instead of a Promise<R2MultipartUpload> from R2Bucket#resumeMultipartUpload(). Thanks @notorca for the PR.
Copy known-lengths from FixedLengthStreams and Request/Response body streams when calling ReadableStream#tee(). Closes issue #506, thanks @notorca.