Convenience functions to work with OpenID Connect

It includes:
- functions to verify with ID tokens (`OIDC.IDToken.verify/3`, `OIDC.IDToken.verify_hash/4` and
- functions to authenticate using OpenID Connect flows (`OIDC.Auth.gen_challenge/1`,
`OIDC.Auth.request_uri/2` and `OIDC.Auth.verify_response/2`)

## Installation

def deps do
    {:oidc, "~> 0.4"},
    {:hackney, "~> 1.0"}

The hackney dependency is used as the default adapter for Tesla. Another one can be used
instead (see
[]( and then
has to be configured in your `config.exs`:

config :tesla, adapter: Tesla.Adapter.AnotherOne