Unable to create a 'DbContext' of type ''. The exception 'Unable to resolve service for type 'Microsoft.EntityFrameworkCore.DbContextOptions`1[WebApiTemplate.Data.Sql.DatabaseContext]' while attempting to activate 'WebApiTemplate.Data.Sql.DatabaseContext'.' was thrown while attempting to create an instance. For the different patterns supported at design time, 

Unable to create a 'DbContext' of type ''. The exception 'Unable to resolve service for type 'Microsoft.EntityFrameworkCore.DbContextOptions`1[WebApiTemplate.Data.Sql.DatabaseContext]' while attempting to activate 'WebApiTemplate.Data.Sql.DatabaseContext'.' was thrown while attempting to create an instance. For the different patterns supported at design time, 

using Microsoft.EntityFrameworkCore;
using WebApiTemplate.Data.Entities;

namespace WebApiTemplate.Data.Sql;

public class DatabaseContext : DbContext
{
    public DatabaseContext(DbContextOptions<DatabaseContext> options) : base(options)
    {
    }   
    public required DbSet<Books> Books { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        if (optionsBuilder.IsConfigured) return;
        var host = Environment.GetEnvironmentVariable("DB_HOST");
        var port = Environment.GetEnvironmentVariable("DB_PORT");
        var user = Environment.GetEnvironmentVariable("DB_USER");
        var password = Environment.GetEnvironmentVariable("DB_PASSWORD");
        var database = Environment.GetEnvironmentVariable("DB_DATABASE");
            
        var connectionString = $"Host={host};Port={port};Username={user};Password={password};Database={database}";
        optionsBuilder.UseNpgsql(connectionString);
    }
}

using Microsoft.EntityFrameworkCore;
using WebApiTemplate.Data.Entities;

namespace WebApiTemplate.Data.Sql;

public class DatabaseContext : DbContext
{
    public DatabaseContext(DbContextOptions<DatabaseContext> options) : base(options)
    {
    }   
    public required DbSet<Books> Books { get; set; }
    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        if (optionsBuilder.IsConfigured) return;
        var host = Environment.GetEnvironmentVariable("DB_HOST");
        var port = Environment.GetEnvironmentVariable("DB_PORT");
        var user = Environment.GetEnvironmentVariable("DB_USER");
        var password = Environment.GetEnvironmentVariable("DB_PASSWORD");
        var database = Environment.GetEnvironmentVariable("DB_DATABASE");
            
        var connectionString = $"Host={host};Port={port};Username={user};Password={password};Database={database}";
        optionsBuilder.UseNpgsql(connectionString);
    }
}