Add microsoft.exchange.webservices.data.credential.BearerTokenCredentials

[kb000]

This should address #579

[codecov-io]

Codecov Report

Merging #606 into master will increase coverage by 0.04%.
The diff coverage is 66.66%.

@@             Coverage Diff              @@
##             master     #606      +/-   ##
============================================
+ Coverage     10.43%   10.47%   +0.04%     
- Complexity        0      473     +473     
============================================
  Files           550      551       +1     
  Lines         20436    20451      +15     
  Branches       2626     2084     -542     
============================================
+ Hits           2132     2142      +10     
- Misses        18151    18154       +3     
- Partials        153      155       +2

Impacted Files	Coverage Δ	Complexity Δ
...rvices/data/credential/BearerTokenCredentials.java	66.66% <66.66%> (ø)	3 <3> (?)

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[dsebastien]

Hello,

Any chance to get this PR merged in the near future?
Am I mistaken if I think that without this, using the https://github.com/bookaroom/ews-java-api/blob/master/src/main/java/microsoft/exchange/webservices/data/credential/TokenCredentials.java is useless and doesn't work?

Currently I try to bind to an email item, but always end up with a 403 unauthorized error...

[kb000]

From what I understand, TokenCredentials.java was designed to be used with a SAML or Kerberos tokens. The heavy lifting is done in WSSecurityBasedCredentials, the base class. I don't know much more about it than that it didn't work for me, living in the OAuth world of 2017.

I found success using AAD to get an OAUTH2 bearer token (e.g. from a POST to https://login.windows.net/common/oauth2/token?api-version=1.0). This PR allows the ews-java-api to pass that token along to the EWS SOAP service.

I was inspired by this StackOverflow answer, where someone was able to use EWS/SOAP directly with a bearer token: https://stackoverflow.com/questions/41875795/office-365-calendar-api-using-ews-and-oauth-2