SP-368-Clarification-on-Default-Value-for-Start-Date-in-Door-Lock-Online-Tile-Limited-Password-repeat-section (#296)

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## Jira Ticket
[SP-368](https://syncrow.atlassian.net/browse/SP-368)

## Description

1. Shows an error dialog when the users sets the start date in create
visitor password that is before current time.
2. Initially sets the Start Date time as now.

## Type of Change

<!--- Put an `x` in all the boxes that apply: -->

- [x] ✨ New feature (non-breaking change which adds functionality)
- [ ] 🛠️ Bug fix (non-breaking change which fixes an issue)
- [ ] ❌ Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] 🧹 Code refactor
- [ ] ✅ Build configuration change
- [ ] 📝 Documentation
- [ ] 🗑️ Chore 


[SP-368]:
https://syncrow.atlassian.net/browse/SP-368?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ

lib/pages/visitor_password/bloc/visitor_password_bloc.dart

@@ -68,7 +68,7 @@ class VisitorPasswordBloc
   DateTime? startTime = DateTime.now();
   DateTime? endTime;
 
-  String startTimeAccess = 'Start Time';
+  String startTimeAccess = DateTime.now().toString().split('.').first;
   String endTimeAccess = 'End Time';
   PasswordStatus? passwordStatus;
   selectAccessType(
@@ -136,6 +136,27 @@ class VisitorPasswordBloc
             );
             return;
           }
+          if(selectedTimestamp < DateTime.now().millisecondsSinceEpoch ~/ 1000) {
+            if(selectedTimestamp < DateTime.now().millisecondsSinceEpoch ~/ 1000) {
+              await showDialog<void>(
+                context: event.context,
+                builder: (context) => AlertDialog(
+                  title: const Text('Effective Time cannot be earlier than current time.'),
+                  actionsAlignment: MainAxisAlignment.center,
+                  content: 
+                    FilledButton(
+                      onPressed: () {
+                        Navigator.of(event.context).pop();
+                        add(SelectTimeVisitorPassword(context: event.context, isStart: true, isRepeat: false));
+                      },
+                      child: const Text('OK'),
+                    ),
+                  
+                ),
+              );
+            }
+            return;
+          }
           effectiveTimeTimeStamp = selectedTimestamp;
           startTimeAccess = selectedDateTime.toString().split('.').first;
         } else {