refactor(infra,api.tests): fix my null lies

src/FiscalOS.Core/Accounts/Account.cs

@@ -4,9 +4,9 @@ public sealed class Account : Entity
 {
   public Guid UserId { get; init; }
   public Guid InstitutionId { get; init; }
-  public Institution Institution { get; init; } = null!;
+  public Institution? Institution { get; init; }
   public string Name { get; init; } = string.Empty;
-  public AccountMetadata Metadata { get; init; } = null!;
+  public AccountMetadata? Metadata { get; init; }
 
   public static Account From(Guid institutionId, string name, AccountMetadata accountMetadata)
   {

src/FiscalOS.Core/Accounts/Institution.cs

@@ -4,7 +4,7 @@ public sealed class Institution : Entity
 {
   public Guid UserId { get; init; }
   public string Name { get; init; } = string.Empty;
-  public InstitutionMetadata Metadata { get; init; } = null!;
+  public InstitutionMetadata? Metadata { get; init; }
 
   private Institution()
   {

tests/FiscalOS.API.Tests/Integration/AddTests.cs

@@ -222,8 +222,8 @@ public class AddTests(TestApi testApi) : IntegrationTest(testApi)
 
     var json = JsonSerializer.Serialize(new
     {
-      plaidInstitutionId = ((PlaidMetadata)institution.Metadata).PlaidId,
-      plaidAccountId = ((PlaidAccountMetadata)account.Metadata).PlaidId,
+      plaidInstitutionId = ((PlaidMetadata)institution.Metadata!).PlaidId,
+      plaidAccountId = ((PlaidAccountMetadata)account.Metadata!).PlaidId,
       plaidAccountName = ((PlaidAccountMetadata)account.Metadata).PlaidName,
     });
     using var content = new StringContent(json, Encoding.UTF8, "application/json");
@@ -270,7 +270,7 @@ public class AddTests(TestApi testApi) : IntegrationTest(testApi)
 
     var json = JsonSerializer.Serialize(new
     {
-      plaidInstitutionId = ((PlaidMetadata)institution.Metadata).PlaidId,
+      plaidInstitutionId = ((PlaidMetadata)institution.Metadata!).PlaidId,
       plaidAccountId = newAccountId,
       plaidAccountName = newAccountName,
     });

tests/FiscalOS.API.Tests/Integration/ConnectTests.cs

@@ -136,7 +136,7 @@ public class ConnectTests(TestApi testApi) : IntegrationTest(testApi)
     var json = JsonSerializer.Serialize(new
     {
       publicToken = "token",
-      plaidInstitutionId = ((PlaidMetadata)institution.Metadata).PlaidId,
+      plaidInstitutionId = ((PlaidMetadata)institution.Metadata!).PlaidId,
     });
     using var content = new StringContent(json, Encoding.UTF8, "application/json");
     using var request = new HttpRequestMessage(HttpMethod.Post, ConnectUri)