Calling to base after override OnModelCreating

Using EFCore with IdentityCore, after override OnModelCreating, you have to call base method to be able to create database for the first time

```csharp
protected override void OnModelCreating(ModelBuilder modelBuilder)
{
modelBuilder.Entity()
.HasKey(t => new { t.PostId, t.CategoryId });
modelBuilder.Entity()
.HasOne(pt => pt.Post)
.WithMany(p => p.PostCategories)
.HasForeignKey(pt => pt.PostId);
modelBuilder.Entity()
.HasOne(pt => pt.Category)
.WithMany(t => t.PostCategories)
.HasForeignKey(pt => pt.CategoryId);
base.OnModelCreating(modelBuilder);
}
```

---
#### Document Details

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* ID: 24b2b50e-35f8-9e0b-8ce5-840e1ea816e6
* Version Independent ID: 9e0e6e2c-48fa-76c3-3bd9-813a6df22645
* Content: [Relationships - EF Core](https://docs.microsoft.com/en-us/ef/core/modeling/relationships)
* Content Source: [entity-framework/core/modeling/relationships.md](https://github.com/aspnet/EntityFramework.Docs/blob/master/entity-framework/core/modeling/relationships.md)
* Product: **entity-framework**
* GitHub Login: @rowanmiller
* Microsoft Alias: **divega**