Refactor SQL execution and enhance envelope creation

- Updated `ISQLExecutor<TEntity>` to inherit from new `ISQLExecutor` interface for improved SQL execution flexibility.
- Added package references for `Dapper` and `DigitalData.Core` in project files.
- Modified `CreateEnvelopeCommand` to include `[BindNever]` on `UserId` for better model binding control.
- Refactored `CreateEnvelopeCommandHandler` to use `DynamicParameters` for SQL parameter handling.
- Updated `CreateEnvelopeSQL` to select only the top record for performance.
- Introduced `GetIdOrDefault` method in `ControllerExtensions` for user ID retrieval with fallback.
- Added `CreateAsync` method in `EnvelopeController` for envelope creation using `IMediator`.
- Ensured infrastructure project has necessary package references.
- Refactored `SQLExecutor` to implement new interface and simplified constructor.
- Introduced `SQLExecutorBaseEntity` for entity-specific SQL command execution.

EnvelopeGenerator.Application/Contracts/SQLExecutor/ISQLExecutor.cs

@@ -5,7 +5,7 @@
 /// Provides abstraction for raw SQL execution as well as mapping the results to <typeparamref name="TEntity"/> objects.
 /// </summary>
 /// <typeparam name="TEntity">The entity type to which the SQL query results will be mapped.</typeparam>
-public interface ISQLExecutor<TEntity>
+public interface ISQLExecutor<TEntity>: ISQLExecutor
 {
     /// <summary>
     /// Executes a raw SQL query and returns an <see cref="IQuery{TEntity}"/> for further querying operations on the result.

EnvelopeGenerator.Application/Contracts/SQLExecutor/ISQLExecutorBaseEntity.cs

@@ -0,0 +1,29 @@
+using Dapper;
+
+namespace EnvelopeGenerator.Application.Contracts.SQLExecutor;
+
+/// <summary>
+/// 
+/// </summary>
+public interface ISQLExecutor
+{
+    /// <summary>
+    /// Executes a raw SQL query and returns an <see cref="IQuery{TEntity}"/> for further querying operations on the result.
+    /// </summary>
+    /// <typeparam name="TEntity">The entity type to which the SQL query results will be mapped.</typeparam>
+    /// <param name="sql">The raw SQL query to execute.</param>
+    /// <param name="parameters">Parameters for the SQL query.</param>
+    /// <param name="cancellation">Optional cancellation token for the operation.</param>
+    /// <returns>An <see cref="IQuery{TEntity}"/> instance for further query operations on the result.</returns>
+    Task<IEnumerable<TEntity>> Execute<TEntity>(string sql, DynamicParameters parameters, CancellationToken cancellation = default);
+
+    /// <summary>
+    /// Executes a custom SQL query defined by a class that implements <see cref="ISQL{TEntity}"/> and returns an <see cref="IQuery{TEntity}"/> for further querying operations on the result.
+    /// </summary>
+    /// <typeparam name="TEntity">The entity type to which the SQL query results will be mapped.</typeparam>
+    /// <typeparam name="TSQL">The type of the custom SQL query class implementing <see cref="ISQL{TEntity}"/>.</typeparam>
+    /// <param name="parameters">Parameters for the SQL query.</param>
+    /// <param name="cancellation">Optional cancellation token for the operation.</param>
+    /// <returns>An <see cref="IQuery{TEntity}"/> instance for further query operations on the result.</returns>
+    Task<IEnumerable<TEntity>> Execute<TEntity, TSQL>(DynamicParameters parameters, CancellationToken cancellation = default) where TSQL : ISQL;
+}