use SQLCipher (#981)

* use SQLCipher

* pass encryption key via CLI options

* update dependencies to use git

* add CONTRIBUTING.md

* move flag, enable build in sqlcipher branch

* update dependencies

docs/rfcs/2022-08-29-database-encryption.md

@@ -0,0 +1,25 @@
+# Database encryption
+
+## Approach
+
+Using SQLCipher - it is a drop in replacement for SQLite that works for non-encrypted databases without any changes (TODO test on iOS/Android).
+
+`direct-sqlite` and `sqlite-simple` libraries are forked and renamed to `direct-sqlcipher` and `sqlcipher-simple`, with replaced cbits in `direct-sqlcipher` (TODO include SQLCipher as git submodule with a script to upgrade cbits).
+
+While SQLCipher provides additional C functions to set and change database key, they do not necessarily need to be exported as they are available as PRAGMAs.
+
+Moving from plaintext to encrypted database (and back) requires migration process using [sqlcipher_export() function](https://discuss.zetetic.net/t/how-to-encrypt-a-plaintext-sqlite-database-to-use-sqlcipher-and-avoid-file-is-encrypted-or-is-not-a-database-errors/868).
+
+The approach would be similar to database migration for the notifications:
+
+1. the current users will be offered to migrate to encrypted database once, with a notice that it can be done later via settings.
+2. the new users will be asked to enter a pass-phrase to create a new database (it can be empty, in which case the database won't be encrypted).
+3. during the migration the database backup will be created and the old database files will be preserved - in case of the app failing to open the new database right after the migration it should revert to using the previous database.
+
+When opening the database the key must be passed via chat command / agent configuration, some test query must be performed to check that the key is correct: https://www.zetetic.net/sqlcipher/sqlcipher-api/#PRAGMA_key
+
+Options to support in chat settings:
+
+- encrypt database (with automatic rollback in case of failure)
+- decrypt database (-"-)
+- change key (using [PRAGMA rekey](https://www.zetetic.net/sqlcipher/sqlcipher-api/#rekey))