How to "extend" EF data model in other assembly

Question

I have solution with structure like this:

Solution
'-Project1
  '-Model1.cs
  '-MainDataContext.cs
'-Project2
  '-Model1.cs
  '-MainDataContext.cs

• Project1 and Project2 are simple assemblies
• Project2 references Project 1
• Both Project1 and Project 2 uses Entity Framework Core 2.2
• Project2.Model1.cs is derived from from Project1.Model1.cs
• Project2.MainDataContext is derived from Project1.MainDataContext
• Both assebmlies will have their own migrations

My plan is to have 2 separate apps where first will be using Project1 assembly and second Project2 assembly. Most (like 98%) of the data-model and business logic will be the same and we can say that Project1 is the "reference" one.

If I add some field specific for Project2 into Poject2.Model1 class and call the Add-Migration on Project2 assembly, the additional field is not detected and empty migration C# script is generated.

EDIT:

In Project1.MainDataContext I've declared:

public virtual DbSet<Model1> Model { get; set; }

In Project2.MainDataContext I've declared:

using Model1 = Project2.Model1;
...
public virtual DbSet<Model1> Model { get; set; }

At running Add-Migration I get Every concrete entity type in the hierarchy needs to have a unique discriminator value. error (which totally makes sense).

Is there possibility to extend Project1.Model1 with Project2.Model1 so there will be 2 separate migrations in both Project1 and Project2 but the table name in DB will be the same for both types?