* Stop using Rust's JoinRule.private in mocks.
It isn't used anywhere else (see MSC4413 for more context).
* Use our own JoinRule (and AllowRule) types.
* Update ElementX/Sources/Services/Room/JoinRule.swift
Co-authored-by: Stefan Ceriu <stefan.ceriu@gmail.com>
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Co-authored-by: Stefan Ceriu <stefan.ceriu@gmail.com>