Implement trust in identity v3 api

Added new module in identity v3 api to handle create, read, and delete
operations of trust resources.

Co-Authored-By: Lance Bragstad <lbragstad@gmail.com>
Co-Authored-By: Steve Martinelli <stevemar@ca.ibm.com>

Closes-Bug: #1413718
Change-Id: I2b360b141ff70d4f396466abede859a3db6644f4

doc/source/command-objects/trust.rst

@@ -0,0 +1,101 @@
+=====
+trust
+=====
+
+Identity v3
+
+trust create
+------------
+
+Create new trust
+
+.. program:: trust create
+.. code:: bash
+
+    os trust create
+        --project <project>
+        --role <role>
+        [--impersonate]
+        [--expiration <expiration>]
+        [--project-domain <domain>]
+        [--trustor-domain <domain>]
+        [--trustee-domain <domain>]
+        <trustor>
+        <trustee>
+
+.. option:: --project <project>
+
+    Project being delegated (name or ID) (required)
+
+.. option:: --role <role>
+
+    Roles to authorize (name or ID) (repeat to set multiple values) (required)
+
+.. option:: --impersonate
+
+    Tokens generated from the trust will represent <trustor> (defaults to False)
+
+.. option:: --expiration <expiration>
+
+    Sets an expiration date for the trust (format of YYYY-mm-ddTHH:MM:SS)
+
+.. option:: --project-domain <domain>
+
+    Domain that contains <project> (name or ID)
+
+.. option:: --trustor-domain <domain>
+
+    Domain that contains <trustor> (name or ID)
+
+.. option:: --trustee-domain <domain>
+
+    Domain that contains <trustee> (name or ID)
+
+.. describe:: <trustor-user>
+
+    User that is delegating authorization (name or ID)
+
+.. describe:: <trustee-user>
+
+    User that is assuming authorization (name or ID)
+
+
+trust delete
+------------
+
+Delete trust(s)
+
+.. program:: trust delete
+.. code:: bash
+
+    os trust delete
+        <trust> [<trust> ...]
+
+.. describe:: <trust>
+
+    Trust(s) to delete
+
+trust list
+----------
+
+List trusts
+
+.. program:: trust list
+.. code:: bash
+
+    os trust list
+
+trust show
+----------
+
+Display trust details
+
+.. program:: trust show
+.. code:: bash
+
+    os trust show
+        <trust>
+
+.. describe:: <trust>
+
+    Trust to display