Prompt to accept integration manager policies on registration

[lampholder]

[lampholder]

If we have #10088 we might not actually want this

[lampholder]

This will require a change to scalar (to expose a policy document) - will this also require a spec change?

[turt2live]

will this also require a spec change?

Technically no, because integration managers are not in the spec yet. I certainly wouldn't mind it being done as a collaborative MSC towards matrix-org/matrix-spec-proposals#1956 (which also has a comment on it saying something about legal documents)

[lampholder]

I'm thinking maybe we shouldn't do this (at least not now) and instead rely on #10167 + #10088 to cover most cases.