MSC1692: Terms of service at registration (#1692)
* Terms of service API proposal
* Alter structures to support multiple languages
This also introduces an ID for clients to internally reference the policies.
* Alter the login process to reflect login's lack of UI auth
* Add a note about MSC2140
* Add a flag to the sync response to indicate the sync is withheld
* Use the soft logout MSC
* Fix headings
* Move non-registration bits out
* Reference MSC3012
* Adjust wording for new scope
* Rewrite to newer modern standards; address feedback from last FCP
* Update proposals/1692-terms-at-registration.md
Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
* Update references
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Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>
