[LucDeCaf]

Reworks the Get/GetAll/GetOptional APIs to be more flexible and performant, at the cost of needing more manual implementation at times.

API Changes

Getter methods now accept a generic parameter T and a SqlMapper<T> mapper delegate, which is now used to construct the method's result types. This allows us to remove Dapper completely and its reflection-heavy approach, which future-proofs the PowerSync SDK for iOS/iPadOS, lets us define our own completely separate API, and should (pending benchmarks) make the query API faster.
Overloads also exist for the new IFromRow<T> interface, which lets users skip passing the mapper to the query function every time.

This also renames and exposes the previously unused QueryResult class/interface to allow for dynamic/mapper-less row access.

This PR also adds a PowerSync.Common.SourceGenerators package, which currently defines the GenerateSqlMapper attribute class. This provides a default, Dapper-style IFromRow<T> implementation for simple classes, which should help users that liked the flexibility and ease-of-use provided by Dapper.

Examples

Using Dapper (old):

using PowerSync.Common;
// using ...

public class Todo
{
  public string Id { get; set; }
  public string ListId { get; set; }
  public DateTime CreatedAt { get; set; }
  public bool Completed { get; set; }
  // ...
}

// Results are obtained using reflection at runtime and rely on Dapper's internal object mapper
T[] result = db.GetAll<Todo>("SELECT * FROM todos WHERE list_id = ?', ["my_list"]);

Using mapper:

using PowerSync.Common;
// using ...

public class Todo
{
  public string Id { get; set; }
  public string ListId { get; set; }
  public DateTime CreatedAt { get; set; }
  public bool Completed { get; set; }
  // ...
}

List<Todo> result = await db.GetAll<T>(
  "SELECT * FROM todos WHERE list_id = ?",
  ["my_list"],
  // Define a mapper function from IQueryRow to T
  (IQueryRow row) => {
    Todo t = new();
    t.Id = row.GetString("id");
    t.ListId = row.GetString("list_id");
    t.CreatedAt = row.GetDateTime("created_at");
    t.Completed = row.GetBool("completed");
    // ...
    return t;
  }
);

Using IFromRow<T>:

using PowerSync.Common;
// using ...

public class Todo : IFromRow<Todo>
{
  public string Id { get; set; }
  public string ListId { get; set; }
  public DateTime CreatedAt { get; set; }
  public bool Completed { get; set; }
  // ...

  // Static method so that an appropriate constructor can be chosen
  public static Todo FromRow(IQueryRow row)
  {
    Todo t = new();
    t.Id = row.GetString("id");
    t.ListId = row.GetString("list_id");
    t.CreatedAt = row.GetDateTime("created_at");
    t.Completed = row.GetBool("completed");
    // ...
    return t;
  }
}

List<Todo> result = await db.GetAll<Todo>("SELECT * FROM todos WHERE list_id = ?", ["my_list"]);

Using source generators:

using PowerSync.Common;
// using ...

// Include the PowerSync source generators
using PowerSync.Common.SourceGenerators;

[GenerateSqlMapper]
public partial class Todo // class must be partial
{
  public string Id { get; set; }
  public string ListId { get; set; }
  public DateTime CreatedAt { get; set; }
  public bool Completed { get; set; }
  // ...
}

// IFromRow<Todo> implementation is automatically generated
List<Todo> result = await db.GetAll<Todo>("SELECT * FROM todos WHERE list_id = ?", ["my_list"]);

AI usage

I manually defined and rewrote the new API in IDBAdapter.cs. Claude Opus 5.5 implemented the required code changes and source generator package, plus added some tests. I will review and verify all changes before marking this as ready for review.