feat(api,core,infra): refactor endpoint routing and add institution account discovery

- Move login and refresh endpoints under a unified /auth route group
- Relocate institution connection logic from /accounts to /institutions
- Implement GET /institutions/{id}/available to fetch real-time Plaid
accounts
- Introduce HttpRequestBuilder utility to streamline integration testing
- Enhance PlaidService with GetAccountsAsync to support account fetching
- Clean up global usings and project structure for better domain
isolation

tests/FiscalOS.API.Tests/Infra/HttpRequestBuilder.cs

@@ -0,0 +1,128 @@
+namespace FiscalOS.API.Tests.Infra;
+
+internal sealed class HttpRequestBuilder
+{
+  private HttpMethod _method = HttpMethod.Get;
+  private Uri? _uri;
+  private object? _body;
+  private string? _bearerToken;
+  private readonly Dictionary<string, string> _cookies = [];
+  private readonly Dictionary<string, string> _headers = [];
+
+  private HttpRequestBuilder()
+  {
+  }
+
+  public static HttpRequestBuilder New() => new();
+
+  public HttpRequestBuilder WithMethod(HttpMethod method)
+  {
+    _method = method;
+    return this;
+  }
+
+  public HttpRequestBuilder WithUri(Uri uri)
+  {
+    _uri = uri;
+    return this;
+  }
+
+  public HttpRequestBuilder WithBody<T>(T body)
+  {
+    _body = body;
+    return this;
+  }
+
+  public HttpRequestBuilder WithBearerToken(string token)
+  {
+    _bearerToken = token;
+    return this;
+  }
+
+  public HttpRequestBuilder WithUserId(Guid userId)
+  {
+    _bearerToken = JwtTokenBuilder.New()
+      .WithClaim(JwtRegisteredClaimNames.Sub, userId.ToString())
+      .Build();
+
+    return this;
+  }
+
+  public HttpRequestBuilder WithCookie(string name, string value)
+  {
+    _cookies[name] = value;
+    return this;
+  }
+
+  public HttpRequestBuilder WithRefreshCookie(string token)
+  {
+    return WithCookie("fiscalos_refresh_cookie", token);
+  }
+
+  public HttpRequestBuilder WithHeader(string name, string value)
+  {
+    _headers[name] = value;
+    return this;
+  }
+
+  public HttpRequestBuilder Post(Uri uri)
+  {
+    _method = HttpMethod.Post;
+    _uri = uri;
+    return this;
+  }
+
+  public HttpRequestBuilder Get(Uri uri)
+  {
+    _method = HttpMethod.Get;
+    _uri = uri;
+    return this;
+  }
+
+  public HttpRequestBuilder Put(Uri uri)
+  {
+    _method = HttpMethod.Put;
+    _uri = uri;
+    return this;
+  }
+
+  public HttpRequestBuilder Delete(Uri uri)
+  {
+    _method = HttpMethod.Delete;
+    _uri = uri;
+    return this;
+  }
+
+  public HttpRequestMessage Build()
+  {
+    if (_uri is null)
+    {
+      throw new InvalidOperationException("URI must be set before building the request.");
+    }
+
+    var request = new HttpRequestMessage(_method, _uri);
+
+    if (_body is not null)
+    {
+      var json = JsonSerializer.Serialize(_body);
+      request.Content = new StringContent(json, Encoding.UTF8, "application/json");
+    }
+
+    if (_bearerToken is not null)
+    {
+      request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", _bearerToken);
+    }
+
+    foreach (var (key, value) in _cookies)
+    {
+      request.Headers.Add("Cookie", $"{key}={value}");
+    }
+
+    foreach (var (key, value) in _headers)
+    {
+      request.Headers.Add(key, value);
+    }
+
+    return request;
+  }
+}

tests/FiscalOS.API.Tests/Infra/SerializableDictionary.cs

@@ -0,0 +1,41 @@
+namespace FiscalOS.API.Tests.Infra;
+
+public interface ISerializableDictionary<TKey, TValue> : IDictionary<TKey, TValue>, IXunitSerializable
+{
+}
+
+public class SerializableDictionary<TKey, TValue> 
+  : Dictionary<TKey, TValue>, ISerializableDictionary<TKey, TValue> where TKey : notnull
+{
+  public SerializableDictionary() { }
+
+  public SerializableDictionary(IDictionary<TKey, TValue> dictionary) : base(dictionary)
+  {
+  }
+
+  public void Deserialize(IXunitSerializationInfo info)
+  {
+    Clear();
+
+    var keysJson = info.GetValue<string>("_DictKeys") ?? "[]";
+    var valuesJson = info.GetValue<string>("_DictValues") ?? "[]";
+    var keys = JsonSerializer.Deserialize<List<TKey>>(keysJson);
+    var values = JsonSerializer.Deserialize<List<TValue>>(valuesJson);
+
+    if (keys is null || values is null || keys.Count != values.Count)
+    {
+      return;
+    }
+
+    for (var i = 0; i < keys.Count; i++)
+    {
+      Add(keys[i], values[i]);
+    }
+  }
+
+  public void Serialize(IXunitSerializationInfo info)
+  {
+    info.AddValue("_DictKeys", JsonSerializer.Serialize(Keys));
+    info.AddValue("_DictValues", JsonSerializer.Serialize(Values));
+  }
+}

tests/FiscalOS.API.Tests/Infra/TestApi.cs

@@ -1,5 +1,3 @@
-using Microsoft.Extensions.Configuration;
-
 namespace FiscalOS.API.Tests.Infra;
 
 public class TestApi : WebApplicationFactory<Program>