Support arbitrary flakerefs in Lockable HTTP Tarball Protocol (Link rel=immutable)

[fgaz]

Is your feature request related to a problem? Please describe.

In the Lockable HTTP Tarball Protocol, there is this restriction:

flakeref must be a tarball flakeref

Because of that, flake versioning services such as rime and flakehub can only support tarball flakes. However, some forges (cgit, phorge, ...) only support git access.

Describe the solution you'd like

The feature could be extended to support arbitrary flakerefs (with restricted parameters).

Describe alternatives you've considered

Additional context

https://github.com/cafkafk/rime/issues/23#issuecomment-2404454380

Priorities

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