Room 2.4.0-alpha04

Room now supports multimap return types @Dao methods, useful for JOIN statements. The supported types of multimaps are Map along with Guava's ImmutableMap, ImmutableSetMultimap and ImmutableListMultimap. androidx.room:room-paging is released, providing native Paging 3.0 support for Room queries returning androidx.paging.PagingSource. Fix an issue in auto migrations regarding handling foreign key violations.