feat: add EF Core layer with entities, configurations and DbContext

- Directory.Packages.props and Directory.Build.props for central package management
- TemplateEntity, ProviderEntity, ProviderUsageEntity (internal to DAL.EF)
- TemplateEntityConfiguration: composite unique index (service_name, key, language_code), Variables as JSON column
- ProviderEntityConfiguration: settings stored as jsonb, index on (service_name, priority)
- ProviderUsageEntityConfiguration: composite unique index (provider_id, date)
- All entities map Id column explicitly as 'id' (snake_case)
- NotificationDbContext with ApplyConfigurationsFromAssembly

Ref: IT-628

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

HrynCo.NotificationService.DAL.EF/Configurations/ProviderEntityConfiguration.cs

@@ -0,0 +1,39 @@
+using HrynCo.NotificationService.DAL.EF.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace HrynCo.NotificationService.DAL.EF.Configurations;
+
+internal class ProviderEntityConfiguration : IEntityTypeConfiguration<ProviderEntity>
+{
+    public void Configure(EntityTypeBuilder<ProviderEntity> builder)
+    {
+        builder.ToTable("providers");
+
+        builder.HasKey(x => x.Id);
+        builder.Property(x => x.Id).HasColumnName("id");
+
+        builder.Property(x => x.ServiceName)
+            .HasColumnName("service_name")
+            .IsRequired()
+            .HasMaxLength(100);
+
+        builder.HasIndex(x => new { x.ServiceName, x.Priority });
+
+        builder.Property(x => x.Priority).HasColumnName("priority");
+
+        builder.Property(x => x.ProviderType).HasColumnName("provider_type");
+
+        builder.Property(x => x.SettingsJson)
+            .HasColumnName("settings")
+            .HasColumnType("jsonb")
+            .IsRequired();
+
+        builder.Property(x => x.DailyLimit).HasColumnName("daily_limit");
+        builder.Property(x => x.MonthlyLimit).HasColumnName("monthly_limit");
+        builder.Property(x => x.WarnThresholdPercent).HasColumnName("warn_threshold_percent");
+        builder.Property(x => x.IsActive).HasColumnName("is_active");
+        builder.Property(x => x.Created).HasColumnName("created");
+        builder.Property(x => x.Updated).HasColumnName("updated");
+    }
+}

HrynCo.NotificationService.DAL.EF/Configurations/ProviderUsageEntityConfiguration.cs

@@ -0,0 +1,25 @@
+using HrynCo.NotificationService.DAL.EF.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace HrynCo.NotificationService.DAL.EF.Configurations;
+
+internal class ProviderUsageEntityConfiguration : IEntityTypeConfiguration<ProviderUsageEntity>
+{
+    public void Configure(EntityTypeBuilder<ProviderUsageEntity> builder)
+    {
+        builder.ToTable("provider_usage");
+
+        builder.HasKey(x => x.Id);
+        builder.Property(x => x.Id).HasColumnName("id");
+
+        builder.Property(x => x.ProviderId).HasColumnName("provider_id");
+
+        builder.HasIndex(x => new { x.ProviderId, x.Date }).IsUnique();
+
+        builder.Property(x => x.Date).HasColumnName("date");
+        builder.Property(x => x.SentCount).HasColumnName("sent_count");
+        builder.Property(x => x.Created).HasColumnName("created");
+        builder.Property(x => x.Updated).HasColumnName("updated");
+    }
+}

HrynCo.NotificationService.DAL.EF/Configurations/TemplateEntityConfiguration.cs

@@ -0,0 +1,56 @@
+using HrynCo.NotificationService.DAL.EF.Entities;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace HrynCo.NotificationService.DAL.EF.Configurations;
+
+internal class TemplateEntityConfiguration : IEntityTypeConfiguration<TemplateEntity>
+{
+    public void Configure(EntityTypeBuilder<TemplateEntity> builder)
+    {
+        builder.ToTable("templates");
+
+        builder.HasKey(x => x.Id);
+        builder.Property(x => x.Id).HasColumnName("id");
+
+        builder.Property(x => x.ServiceName)
+            .HasColumnName("service_name")
+            .IsRequired()
+            .HasMaxLength(100);
+
+        builder.Property(x => x.Key)
+            .HasColumnName("key")
+            .IsRequired()
+            .HasMaxLength(100);
+
+        builder.Property(x => x.LanguageCode)
+            .HasColumnName("language_code")
+            .IsRequired()
+            .HasMaxLength(10);
+
+        builder.HasIndex(x => new { x.ServiceName, x.Key, x.LanguageCode })
+            .IsUnique();
+
+        builder.Property(x => x.Subject)
+            .HasColumnName("subject")
+            .IsRequired();
+
+        builder.Property(x => x.HtmlBody)
+            .HasColumnName("html_body")
+            .IsRequired();
+
+        builder.Property(x => x.TextBody)
+            .HasColumnName("text_body")
+            .IsRequired();
+
+        builder.Property(x => x.Created).HasColumnName("created");
+        builder.Property(x => x.Updated).HasColumnName("updated");
+
+        builder.OwnsMany(x => x.Variables, v =>
+        {
+            v.ToJson("variables");
+            v.Property(x => x.Name).HasJsonPropertyName("name");
+            v.Property(x => x.Required).HasJsonPropertyName("required");
+        });
+    }
+}