Support Non-Hash Auth Code Redirects

Expected Behavior

I can handled an auth code redirect with a query string, not just a hash.

[REQUIRED] Describe expected behavior

When I call completeAuthorizationRequestIfPossible i'd like it to look at the query string if some configuration option is set.

This line: https://github.com/openid/AppAuth-JS/blob/c30f85e490ab41c9f1e8f8ee05bfdfe964e08626/src/redirect_based_handler.ts#L100 it'd be cool if could handle query strings or hashes.

Describe the problem

See above. My oauth server returns query strings, not hashes. Would like to be able to use this library in browser.

[REQUIRED] Actual Behavior

Second half of the oauth flow never completes, since the code, state, etc, are all in the query string, not hash.

[REQUIRED] Steps to reproduce the behavior

Use an oauth server that sends back an auth code response in a query string.

[REQUIRED] Environment

• AppAuth-JS version: 1.3.1
• AppAuth-JS Environment (Node, Browser (UserAgent), ...):Browser
• Source code snippts (inline or JSBin)

Start at src/redirect_based_handler.ts around the referenced completeAuthorizationRequestIfPossible call. Trace how browser redirects currently read the hash and determine how the requested configuration option should select query-string handling. Done means an OAuth authorization-code redirect carrying code and state in the query string completes the flow as well as the existing hash form.