More work on federation

Cargo.toml

@@ -17,7 +17,7 @@ ruma-client-api = { git = "https://github.com/ruma/ruma-client-api.git" }
 ruma-identifiers = "0.15.1"
 ruma-api = "0.16.0-rc.1"
 ruma-events = "0.19.0"
-ruma-signatures = { git = "https://github.com/ruma/ruma-signatures.git" }
+ruma-signatures = { path = "../ruma-signatures" }
 ruma-federation-api = { path = "../ruma-federation-api" }
 pretty_env_logger = "0.4.0"
 log = "0.4.8"
@@ -30,3 +30,4 @@ tokio = { version = "0.2.18", features = ["macros"] }
 rand = "0.7.3"
 rust-argon2 = "0.8.2"
 reqwest = "0.10.4"
+base64 = "0.12.0"