T2(customer): add EF Core persistence with ORM config and initial migration

[devin-ai-integration]

Summary

Configures CustomerDbContext with ORM mappings ported verbatim from the monolith, generates the initial EF Core migration, and wires up EnsureCreated on startup.

DbContext changes (CustomerDbContext.cs):

using Entities = Customer.Domain.Entities; // alias to disambiguate from root `Customer` namespace

public DbSet<Entities.Customer> Customers => Set<Entities.Customer>();

modelBuilder.Entity<Entities.Customer>(entity => {
    entity.ToTable("AppCustomers");
    entity.Property(c => c.Name).IsRequired().HasMaxLength(100);
    entity.HasIndex(c => c.Name);
    entity.Property(c => c.Email).HasMaxLength(100);
    entity.Property(c => c.PhoneNumber).IsUnicode(false).HasMaxLength(30);
    entity.Property(c => c.City).HasMaxLength(50);
    entity.Property(c => c.CreatedBy).HasMaxLength(40);
    entity.Property(c => c.UpdatedBy).HasMaxLength(40);
});

Startup (Program.cs): adds db.Database.EnsureCreated() in a scoped block after builder.Build(), matching the Notification service pattern.

Migration: InitialCreate creates AppCustomers table with PK, all columns with correct types/constraints, and IX_AppCustomers_Name index.

Verified against PostgreSQL 16 — migration applies cleanly and produces the expected schema.

Part of the Customer microservice carve-out stacked PR chain (T2/T5).

Link to Devin session: https://partner-workshops.devinenterprise.com/sessions/df4fd98794c34738bf5a70c588276dcb
Requested by: @mbatchelor81

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[devin-ai-integration]

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[devin-ai-integration]

Devin Review found 1 potential issue.

[devin-ai-integration]

🔴 Database setup method conflicts with migrations, making future schema updates fail

The database is created using a shortcut method (EnsureCreated() at src/Services/Customer/Customer.API/Program.cs:19) instead of applying the migrations that the PR also introduces, so the migration history table is never populated and any future migration will crash because the tables already exist.

Impact: After the first startup, all subsequent schema migrations will fail with "table already exists" errors, making the migration files in this PR useless.

EnsureCreated vs Migrate conflict mechanism

db.Database.EnsureCreated() creates the schema directly without recording anything in the __EFMigrationsHistory table. The PR also adds a full EF Core migration (src/Services/Customer/Customer.Infrastructure/Data/Migrations/20260626044302_InitialCreate.cs) which expects to be tracked in that history table.

When a developer later adds a second migration and runs db.Database.Migrate() or dotnet ef database update, EF Core will see no migration history and attempt to apply InitialCreate, which will fail because the AppCustomers table already exists.

The RECON.md at src/Services/Customer/RECON.md:115 states the T2 validation gate requires: "EF migration applies against PostgreSQL" — this cannot work with EnsureCreated().

The fix is to replace db.Database.EnsureCreated() with db.Database.Migrate() so the migration is applied and tracked properly.

Suggested change

	db.Database.EnsureCreated();
	db.Database.Migrate();

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[devin-ai-integration]

Valid point about EnsureCreated() vs Migrate() for long-term migration tracking. However, this follows the existing pattern used by the Notification service (Notification.API/Program.cs:26) and was explicitly requested in the task spec. Deferring to the task author on whether to switch to Migrate() in a follow-up.