Split SimpleFIN connections by institution

Group discovered SimpleFIN accounts by institution and create a
separate SyncConnection per institution so each bank appears as
its own card in the UI.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/Purrse.Api/Controllers/BankSyncController.cs

@@ -59,7 +59,7 @@ public class BankSyncController : ControllerBase
         => Ok(await _bankSyncService.CompletePlaidLinkAsync(UserId, request));
 
     [HttpPost("simplefin/connect")]
-    public async Task<ActionResult<SyncConnectionResponse>> ConnectSimpleFin(CreateSimpleFinConnectionRequest request)
+    public async Task<ActionResult<List<SyncConnectionResponse>>> ConnectSimpleFin(CreateSimpleFinConnectionRequest request)
         => Ok(await _bankSyncService.CreateSimpleFinConnectionAsync(UserId, request));
 
     [HttpGet("connections/{id}/discover-accounts")]

src/Purrse.Api/Services/BankSyncService.cs

@@ -180,41 +180,54 @@ public class BankSyncService : IBankSyncService
 
     // --- SimpleFIN Flow ---
 
-    public async Task<SyncConnectionResponse> CreateSimpleFinConnectionAsync(Guid userId, CreateSimpleFinConnectionRequest request)
+    public async Task<List<SyncConnectionResponse>> CreateSimpleFinConnectionAsync(Guid userId, CreateSimpleFinConnectionRequest request)
     {
         var accessUrl = await _simpleFin.ExchangeSetupTokenAsync(request.SetupToken);
 
         var config = new Dictionary<string, string> { ["AccessUrl"] = accessUrl };
         var accounts = await _simpleFin.GetAccountsAsync(config);
-        var institutionName = accounts.FirstOrDefault()?.Institution ?? "SimpleFIN Connection";
+        var encryptedAccessUrl = _encryption.Encrypt(accessUrl);
 
-        var connection = new SyncConnection
+        var groupedByInstitution = accounts.GroupBy(a => a.Institution ?? "SimpleFIN Connection");
+        var connectionIds = new List<Guid>();
+
+        foreach (var group in groupedByInstitution)
         {
-            Id = Guid.NewGuid(),
-            UserId = userId,
-            Provider = SyncProvider.SimpleFIN,
-            InstitutionName = institutionName,
-            EncryptedAccessToken = _encryption.Encrypt(accessUrl)
-        };
-
-        _db.SyncConnections.Add(connection);
-
-        foreach (var account in accounts)
-        {
-            _db.LinkedAccounts.Add(new LinkedAccount
+            var connection = new SyncConnection
             {
                 Id = Guid.NewGuid(),
-                SyncConnectionId = connection.Id,
-                ExternalAccountId = account.ExternalId,
-                ExternalAccountName = account.Name,
-                ExternalAccountType = account.AccountType,
-                LastKnownBalance = account.Balance
-            });
+                UserId = userId,
+                Provider = SyncProvider.SimpleFIN,
+                InstitutionName = group.Key,
+                EncryptedAccessToken = encryptedAccessUrl
+            };
+
+            _db.SyncConnections.Add(connection);
+            connectionIds.Add(connection.Id);
+
+            foreach (var account in group)
+            {
+                _db.LinkedAccounts.Add(new LinkedAccount
+                {
+                    Id = Guid.NewGuid(),
+                    SyncConnectionId = connection.Id,
+                    ExternalAccountId = account.ExternalId,
+                    ExternalAccountName = account.Name,
+                    ExternalAccountType = account.AccountType,
+                    LastKnownBalance = account.Balance
+                });
+            }
         }
 
         await _db.SaveChangesAsync();
 
-        return await GetConnectionAsync(userId, connection.Id);
+        var results = new List<SyncConnectionResponse>();
+        foreach (var id in connectionIds)
+        {
+            results.Add(await GetConnectionAsync(userId, id));
+        }
+
+        return results;
     }
 
     // --- Account Linking ---