Add Clinics database context

Clinics.Backend/Persistence/Context/ClinicsDbContext.cs

+using Microsoft.EntityFrameworkCore;
+
+namespace Persistence.Context;
+
+public partial class ClinicsDbContext : DbContext
+{
+    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
+    {
+        // TODO: Use options pattern
+        optionsBuilder.UseSqlServer("server=.\\;database=Clinics_Test;Trusted_Connection=True; Encrypt=False;MultipleActiveResultSets=true");
+    }
+
+    protected override void OnModelCreating(ModelBuilder modelBuilder)
+    {
+        modelBuilder.ApplyConfigurationsFromAssembly(typeof(ClinicsDbContext).Assembly);
+    }
+}