Implements the device authorisation flow

[ljyanesm]

• Adds support for OAuth 2.0 Device Authorization Grant
• Updates core/mod.rs to include the new CoreDeviceAuthorizationResponse type
• Updates lib.rs to provide access to DeviceAuthorizationUrl and DeviceAuthorizationRequest types
• Adds set_device_authorization_uri method to the Client API to set the URL for contacting the device authorization endpoint
• Implements an example that showcases the process of using the device grant flow to obtain an ID token from the Okta provider. The example demonstrates device code exchange for an access token.

Solves #113

[codecov[bot]]

Codecov Report

Merging #114 (a2af2d2) into main (eb15817) will decrease coverage by 0.49%. The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #114      +/-   ##
==========================================
- Coverage   73.92%   73.43%   -0.49%     
==========================================
  Files          17       17              
  Lines        4092     4107      +15     
==========================================
- Hits         3025     3016       -9     
- Misses       1067     1091      +24     

Impacted Files	Coverage Δ
src/core/mod.rs	53.76% <ø> (ø)
src/lib.rs	66.66% <0.00%> (-6.21%)	:arrow_down:

[ramosbugs]

thanks!