Upgrade rust to use 2021 edition

FlorentinDUBOIS · FlorentinDUBOIS · commit a6fd1f46128e · 2021-10-21T17:37:52.000+02:00
diff --git a/Cargo.toml b/Cargo.toml
@@ -2,7 +2,7 @@
 name = "oauth10a"
 description = "A rust implementation of the oauth 1.0a protocol fully-async with logging, metrics and tracing facilities"
 version = "1.1.0"
-edition = "2018"
+edition = "2021"
 authors = ["Florentin Dubois <florentin.dubois@clever-cloud.com>"]
 license-file = "LICENSE"
 readme = "README.md"
