feat(api): validate account institution is connected and allow adding new account

src/FiscalOS.API/Accounts/Add/Endpoint.cs

@@ -1,3 +1,5 @@
+using FiscalOS.Core.Accounts;
+
 namespace FiscalOS.API.Accounts.Add;
 
 internal static class Endpoint
@@ -19,6 +21,7 @@ internal static class Endpoint
     var userId = httpContext.GetUserId();
 
     var user = await appDbContext.Users
+      .Include(u => u.Institutions.Where(i => i.Metadata is PlaidMetadata && ((PlaidMetadata)i.Metadata).PlaidId == request.PlaidInstitutionId))
       .Include(u => u.Accounts.Where(a => a.Metadata is PlaidAccountMetadata && ((PlaidAccountMetadata)a.Metadata).PlaidId == request.PlaidAccountId))
       .ThenInclude(a => a.Metadata)
       .SingleOrDefaultAsync(u => u.Id == userId, ct);
@@ -28,13 +31,24 @@ internal static class Endpoint
       return Results.Unauthorized();
     }
 
+    if (user.Institutions.Any() is false)
+    {
+      return Results.ValidationProblem(new Dictionary<string, string[]>
+      {
+        ["PlaidInstitutionId"] = ["The PlaidInstitutionId field is invalid. No institution connected with the given PlaidInstitutionId was found for the user."],
+      });
+    }
+
     if (user.Accounts.Any())
     {
       return Results.Conflict();
     }
 
-    // TODO: This is new account
-    // so we should add to the database
+    var accountMetadata = PlaidAccountMetadata.From(request.PlaidAccountId, request.PlaidAccountName);
+    var account = Account.From(user.Institutions.First().Id, request.PlaidAccountName, accountMetadata);
+    user.AddAccount(account);
+
+    await appDbContext.SaveChangesAsync(ct);
 
     return Results.Ok();
   }