Update API endpoints to support Meeting Admin page

• Add endpoint to get attendees for meeting (this makes a database query for each attendee -- is there an easy way to fetch member names for all attendees in 1 query using this ORM?)
• Add endpoint to remove attendee
• Update search endpoint to allow specifying both first name and last name
• Update search endpoint to only match prefixes, instead of finding match anywhere in name or email
• Set default search page size to 10 so it doesn't throw error when page_size is not specified
• Prevent creating multiple meetings with the same name
• Prevent adding a member as an attendee to a meeting multiple times