Add support to authenticate with application credential

[zioproto]

For #1214

Links to the line numbers/files in the OpenStack source code that support the
code in this PR:

• https://github.com/openstack/keystoneauth/blob/stable/rocky/keystoneauth1/identity/v3/application_credential.py#L48-L67
• https://github.com/openstack/keystone/blob/stable/rocky/keystone/conf/constants.py#L20
• https://github.com/openstack/python-keystoneclient/blob/stable/rocky/keystoneclient/v3/application_credentials.py#L42

[theopenlab-ci]

Build succeeded.

• gophercloud-unittest : SUCCESS in 3m 30s
• gophercloud-acceptance-test : SUCCESS in 1h 07m 14s

[jtopjian]

@zioproto Travis is flagging a go fmt error. If you can, run go fmt on the changed files - that should fix things up.

[coveralls]

Coverage decreased (-3.4%) to 75.955% when pulling ea7289e on zioproto:application_credential into 4014077 on gophercloud:master.

[theopenlab-ci]

Build succeeded.

• gophercloud-unittest : SUCCESS in 4m 08s
• gophercloud-acceptance-test : SUCCESS in 1h 51m 11s

[theopenlab-ci]

Build succeeded.

• gophercloud-unittest : SUCCESS in 3m 33s
• gophercloud-acceptance-test : SUCCESS in 1h 02m 40s

[theopenlab-ci]

Build succeeded.

• gophercloud-unittest : SUCCESS in 4m 09s
• gophercloud-acceptance-test : SUCCESS in 48m 57s

[zioproto]

@RdL87 I pushed a new version of the patch that works with any possible combination of ID or NAME env vars. Can you review it ? Are you working on the tests ?

[RdL87]

@zioproto i'm working on this just now. So i'm going to recompile the client with the new library you've just pushed. I will ping you as soon as the keystone becomes available.

[theopenlab-ci]

Build succeeded.

• gophercloud-unittest : SUCCESS in 3m 50s
• gophercloud-acceptance-test : SUCCESS in 1h 13m 22s

[zioproto]

@jtopjian I believe we are ready for review. I added two tests. I tried to to give correct code pointers to keystone codebase. thank you

[theopenlab-ci]

Build succeeded.

• gophercloud-unittest : SUCCESS in 9m 10s
• gophercloud-acceptance-test : SUCCESS in 47m 45s

[jtopjian]

@zioproto This is looking really good. :)

I think I found a good keystone reference to use: https://github.com/openstack/keystoneauth/blob/ebe781a3ea0386d6ff088a84e8dde26e538b856d/keystoneauth1/identity/v3/application_credential.py#L48-L67

It looks to match up really well with your other investigations.

The core functionality of this PR looks correct. The comments I left are just putting some final touches on things.

Let me know if you have any questions :)

[jtopjian]

Let's replace the above URL with:

https://github.com/openstack/keystoneauth/blob/ebe781a3ea0386d6ff088a84e8dde26e538b856d/keystoneauth1/identity/v3/application_credential.py#L48-L67

[zioproto]

Thanks for the review. I pushed changes that should address all the points of the review

[theopenlab-ci]

Build succeeded.

• gophercloud-unittest : SUCCESS in 3m 50s
• gophercloud-acceptance-test : SUCCESS in 1h 03m 41s

[zioproto]

@jtopjian I am not sure what the problem with the coveralls test not passing

[jtopjian]

@zioproto You can ignore Coveralls. It acts weird sometimes.

[jtopjian]

LGTM!

@zioproto @RdL87 Thank you both for your work on this.