No context type was found in the assembly
I eventually found the answer in this question. Basically, in the Package Manager Console there's a "Default project" dropdown. You need to set this to the project that contains your EF context.
I found similar post: Enable Migrations with Context in Separate Assembly?
Example:
enable-migrations -ContextProjectName MyProject.DBContexts -contexttypename MyProject.DBContexts.MyContextName -Verbose
For whom who made this mistake like I did:
Your context class must inherits from DbContext, just like that:
public class DirectorRequestContext : DbContext{ public DbSet<DirectorRequest> DirectorRequests { get; set; }}