The latest version of the ios tus client does not support the upload-metadata header for tus requests. A PR was merged back in September to support this, but a new version has not been released. Wondering when we can expect a new version.
Relevant issue: Metadata field regression · Issue #138 · tus/TUSKit · GitHub
Merged PR that fixes issue: Fix problem with missing custom headers in request · tus/TUSKit@d121656 · GitHub