#1 — Problem with custom fields username and password

When using the 1.0b2 (SVN/UNRELEASED) version of collective.salesforce.authplugin, I got the following error:

Traceback (innermost last):
  Module ZPublisher.Publish, line 110, in publish
  Module ZPublisher.BaseRequest, line 583, in traverse
  Module Products.PluggableAuthService.PluggableAuthService, line 233, in validate
  Module Products.PluggableAuthService.PluggableAuthService, line 600, in _extractUserIds
  Module collective.salesforce.authplugin.mixins.authmixin, line 54, in authenticateCredentials
  Module Products.salesforcebaseconnector.salesforcebaseconnector, line 161, in query
  Module beatbox.python_client, line 148, in query
  Module beatbox._beatbox, line 68, in query
  Module beatbox._beatbox, line 325, in post
SoapFaultError: 'INVALID_FIELD' "INVALID_FIELD: select UserName__c,Password__c from Contact ^ ERROR at Row:1:Column:8 No such column 'UserName__c' on entity 'Contact'. If you are attempting to use a custom field, be sure to append the '__c' after the custom field name. Please reference your WSDL or the describe call for the appropriate names."

When I tried to change it in the ZMI, I continued to get the error:
We're sorry, but there seems to be an error…
The error has been logged as entry number 1230009272.260.21554668451

And I was not able to get access to my Plone site.

I quickly realized that I had swapped the field names and used "username" and "password" in Salesforce, when I should have been using UserName__c and Password__c.

The documentation on the /acl_users/salesforceauthmultiplugin page is not very clear, as it states:
Salesforce.com fields which map to Plone's "username" and "password" fields formatted like the following:
password|Password__c
username|UserName__c

which makes me think that the Salesforce.com fields are the first ones and the Plone fields are the second. I think simply clarifying that the Salesforce fields are Password__c and UserName__c would make this ambiguity go away.

The documentation on this page isn't really any more clear. https://svn.plone.org/[…]/INSTALL.txt

When I tried to make the field Password__c in Salesforce, I got the following error:
Error: The custom field name you provided Password__c on object Contact can only contain alphanumeric characters, must begin with a letter, cannot end with an underscore or contain two consecutive underscore characters, and must be unique across all Contact fields

But I was able to make a field Password_c (with just one underscore), but then I get the error above stating that all custom fields must end with __c.
So now I'm back to square one. Any ideas?