Refactor SQL execution classes into new namespace

Restructure and refactor classes related to SQL execution within the `EnvelopeGenerator.Infrastructure` namespace. Key changes include:
- Added `EnvelopeGenerator.Infrastructure.Executor` namespace.
- Moved and redefined `Query`, `QueryExtension`, `SQLExecutor`, `SQLExecutorBaseEntity`, and `SQLExecutorParams` classes to the new namespace.
- Maintained existing functionality while improving code organization and clarity.

EnvelopeGenerator.Infrastructure/Executor/SQLExecutor.cs

@@ -0,0 +1,33 @@
+using Dapper;
+using EnvelopeGenerator.Application.Contracts.SQLExecutor;
+using Microsoft.Data.SqlClient;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+
+namespace EnvelopeGenerator.Infrastructure.Executor;
+
+public class SQLExecutor : ISQLExecutor
+{
+    private readonly SQLExecutorParams _params;
+
+    private readonly IServiceProvider _provider;
+
+    public SQLExecutor(IServiceProvider provider, IOptions<SQLExecutorParams> sqlExecutorParamsOptions)
+    {
+        _provider = provider;
+        _params = sqlExecutorParamsOptions.Value;
+    }
+
+    public async Task<IEnumerable<TEntity>> Execute<TEntity>(string sql, DynamicParameters parameters, CancellationToken cancellation = default)
+    {
+        using var connection = new SqlConnection(_params.ConnectionString);
+        await connection.OpenAsync(cancellation);
+        return await connection.QueryAsync<TEntity>(sql, parameters);
+    }
+
+    public Task<IEnumerable<TEntity>> Execute<TEntity, TSQL>(DynamicParameters parameters, CancellationToken cancellation = default) where TSQL : ISQL
+    {
+        var sql = _provider.GetRequiredService<TSQL>();
+        return Execute<TEntity>(sql.Raw, parameters, cancellation);
+    }
+}