Band Manager App
Manager has_many :bands - username - email - password_digest - uid - provider
Band belongs_to :manager has_many :band_members has_many :members, through: :band_members - name - manager_id
BandMember belongs_to :band belongs_to :member - instrument - band_id - member_id
Member has_many :band_members has_many :bands, through: :band_members - name