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This should come from the database, and PNI sigs should only be generated when necessary. _Originally posted by @rubdos in https://github.com/whisperfish/presage/pull/245#discussion_r1536765922_

Rework on-boarding

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The on-boarding of new users is not smooth enough. Some problems: 1. Config file needs to be created manually. 2. Config file contains the phone number even though it is...

Contacts are now returned in the receiving messages stream.

Selected messages have wrong offset behind a date separator

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In particular, * quote of a such selected message quotes a wrong message, * opening a link selected message does not work.

As defined in #[rfc9000]. Also use this type (with an internal thin wrapper `ContentLength`) when encoding/deconding the content length of vectors. [rfc9000]: https://www.rfc-editor.org/rfc/rfc9000#name-variable-length-integer-enc