upload-npm : support authToken argument

Support setting authToken to use a token for upload rather than
username/password.

This is "based" on Id0c47d088d6e8febbae3c96caecc81ebe247754e which
does the same for pypi.  There we run a test by uploading to the test
pypi server, I'm not aware of a similar thing for npm.

Change-Id: Ie8610bdfaa33b2120a61802c12e6ba534fe55464

roles/upload-npm/README.rst

@@ -17,6 +17,13 @@ Upload javascript packages to npm
 
      Password to use to log in to npm.
 
+  .. zuul:rolevar:: authToken
+
+     An auth token (issued from the npm server) to authenticate with.
+     This is required if you are using two-factor authentication.  If
+     specifying an authToken you should not specify ```username`` and
+     ``password``.
+
   .. zuul:rolevar:: email
 
      Email associated with the npm account.

roles/upload-npm/tasks/main.yaml

@@ -1,3 +1,10 @@
+- name: Validate password/token combo
+  fail:
+    msg: 'Specify either username/password or authToken'
+  when: >
+      (npm_credentials.authToken is defined) and
+      ((npm_credentials.username is defined) or (npm_credentials.password is defined))
+
 # This is not optimized, but allows for getting a version of node in the
 # home dir.
 - name: Create .npmrc configuration file

roles/upload-npm/templates/.npmrc.j2

@@ -4,7 +4,10 @@ init.author.url={{ npm_credentials.author_url }}
 tag-version-prefix=
 sign-git-tag=true
 
+{% if npm_credentials.username is defined %}
 //registry.npmjs.org/:username={{ npm_credentials.username }}
 //registry.npmjs.org/:_password={{ npm_credentials.password }}
-
+{% else %}
+//registry.npmjs.org/:_authToken={{ npm_credentials.authToken }}
+{% endif %}
 //registry.npmjs.org/:email={{ npm_credentials.author_email }}