refactor: split database into multiple files, more error handling, cleaner code

Cargo.toml

@@ -19,7 +19,6 @@ ruma-api = "0.16.0-rc.3"
 ruma-events = "0.21.0-beta.1"
 ruma-signatures = { git = "https://github.com/ruma/ruma-signatures.git" }
 ruma-federation-api = { git = "https://github.com/ruma/ruma-federation-api.git" }
-pretty_env_logger = "0.4.0"
 log = "0.4.8"
 sled = "0.31.0"
 directories = "2.0.2"
@@ -31,3 +30,4 @@ rand = "0.7.3"
 rust-argon2 = "0.8.2"
 reqwest = "0.10.4"
 base64 = "0.12.0"
+thiserror = "1.0.16"