Allow new members to be added to the "general" committee right when they're made
@DSASanFrancisco/portal-members
SUMMARY https://trello.com/c/MGM3ZPUT/161-create-member-feature-should-allow-you-to-add-the-member-role
When admins add new members manually, they almost always are DSA National members. So then we email them the "welcome" email, but they don't have DSA National membership, so they see that they are not eligible to vote, etc.
This PR upgrades the Member creation API to let admins mark members as DSA National members right at creation time, so that they are properly marked by the time we send them the welcome email
UI PR needed to actually start sending up this field
Edited by David Kettler