add-entity

name	add-entity
description	Add a domain entity/aggregate with EF configuration and a migration to an existing FSH module. Use when adding a new database-backed entity. Pairs with add-feature and create-migration.
argument-hint	[ModuleName] [EntityName]

Add Entity

Rich domain model: sealed aggregate, private EF ctor, static factory, behavior via methods, domain events. DB conventions: .agents/rules/database.md.

Entity — AggregateRoot<Guid> (or BaseEntity<Guid>)

BaseEntity<TId> gives only Id + domain-event machinery. Audit/tenant/soft-delete are opt-in via marker interfaces (the base does NOT carry those fields). New ids use Guid.CreateVersion7().

public sealed class {Entity} : AggregateRoot<Guid>, IHasTenant, IAuditableEntity, ISoftDeletable
{
    public string Name { get; private set; } = default!;
    public Money Price { get; private set; } = default!;

    // IHasTenant
    public string TenantId { get; private set; } = default!;
    // IAuditableEntity
    public DateTimeOffset CreatedOnUtc { get; set; }
    public string? CreatedBy { get; set; }
    public DateTimeOffset? LastModifiedOnUtc { get; set; }
    public string? LastModifiedBy { get; set; }
    // ISoftDeletable
    public bool IsDeleted { get; set; }
    public DateTimeOffset? DeletedOnUtc { get; set; }
    public string? DeletedBy { get; set; }

    private {Entity}() { }   // EF

    public static {Entity} Create(string name, Money price)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(name);
        ArgumentNullException.ThrowIfNull(price);

        var entity = new {Entity} { Id = Guid.CreateVersion7(), Name = name.Trim(), Price = price };
        entity.AddDomainEvent(DomainEvent.Create((id, ts) =>
            new {Entity}CreatedDomainEvent(entity.Id, entity.Name, id, ts)));
        return entity;
    }

    public void Rename(string name)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(name);
        Name = name.Trim();
    }
}

Notes: setters are private set; TenantId/audit/soft-delete members are settable by the framework (interceptor + Finbuckle) so they aren't private set. Use Guid.CreateVersion7(), never Guid.NewGuid().

Domain event — inherit DomainEvent (abstract record)

public sealed record {Entity}CreatedDomainEvent(
    Guid {Entity}Id, string Name, Guid EventId, DateTimeOffset OccurredOnUtc)
    : DomainEvent(EventId, OccurredOnUtc);

Raise with the DomainEvent.Create((id, ts) => …) helper + AddDomainEvent(...) (not QueueDomainEvent).

EF configuration

public sealed class {Entity}Configuration : IEntityTypeConfiguration<{Entity}>
{
    public void Configure(EntityTypeBuilder<{Entity}> builder)
    {
        ArgumentNullException.ThrowIfNull(builder);
        builder.ToTable("{Entities}");                       // schema is set once on the DbContext
        builder.HasKey(x => x.Id);
        builder.Property(x => x.Name).IsRequired().HasMaxLength(200);

        // soft-deletable unique field → filter on live rows only
        builder.HasIndex(x => x.Name).IsUnique().HasFilter("\"IsDeleted\" = FALSE");

        // owned value object
        builder.OwnsOne(x => x.Price, m =>
        {
            m.Property(p => p.Amount).HasColumnName("PriceAmount").HasPrecision(18, 4);
            m.Property(p => p.Currency).HasColumnName("PriceCurrency").HasMaxLength(3);
        });

        builder.Ignore(x => x.DomainEvents);
    }
}

• Do NOT add a manual HasQueryFilter for soft-delete or tenant — BaseDbContext applies both automatically.
• A child entity reached only via a parent nav-collection needs builder.Property(x => x.Id).ValueGeneratedNever() in its config, or EF inserts it as Modified → 0-row UPDATE. See database.md.

Register in the module DbContext

Add a DbSet; configurations are picked up by ApplyConfigurationsFromAssembly:

public DbSet<{Entity}> {Entities} => Set<{Entity}>();

The DbContext already extends BaseDbContext and calls base.OnModelCreating last — don't change that.

Migration

Use the create-migration skill (build first, correct --context):

dotnet ef migrations add Add{Entity} \
  --project src/Host/FSH.Starter.Migrations.PostgreSQL \
  --startup-project src/Host/FSH.Starter.Api \
  --context {X}DbContext

Checklist

• sealed, AggregateRoot<Guid> (+ IHasTenant/IAuditableEntity/ISoftDeletable as needed), private ctor, static Create using Guid.CreateVersion7()
• Domain event inherits DomainEvent; raised via DomainEvent.Create + AddDomainEvent
• EF config: no manual soft-delete/tenant filter; ValueGeneratedNever() on nav-collection children
• DbSet added; build green; migration created with --context {X}DbContext