Develop first version (#1)

Create first version of the library

The code is mainly taken from

* https://gitea.communiquons.org/pierre/oidc-test-client
* https://gitea.communiquons.org/pierre/BasicOIDC

with little improvements.

Reviewed-on: #1

.drone.yml

@@ -0,0 +1,15 @@
+---
+kind: pipeline
+type: docker
+name: default
+
+steps:
+- name: cargo_check
+  image: rust
+  commands:
+  - rustup component add clippy
+  - cargo clippy --all-features -- -D warnings
+  - cargo clippy -- -D warnings
+  - cargo test --all-features
+
+