wip(importing): partial fixes — presentation lookup + presenter gate (broken, needs rework)

Session field column-presence fixes are solid. Presentation lookup no longer
requires presentation_name to find existing records. Presenter gate broadened
to run lookup even without explicit code. Presenter INSERT still broken —
reverted field changes after IntegrityError issue; email-only column guard kept.

Do not rely on this state for presenter creation. Needs rework from c9c69ec.

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

app/routers/event_importing.py

@@ -656,7 +656,7 @@ async def event_importing_program_data(
         event_session_data = {}
         if record.get('session_code'):
             event_session_data['code'] = record.get('session_code', '').strip()
-        else:
+        elif 'session_code' in record:
             event_session_data['code'] = None
         event_session_data['event_id'] = event_id # INSERT and UPDATE the event_id just in case
         event_session_data['event_location_id'] = event_location_id # INSERT and UPDATE the event_location_id in case the session was moved
@@ -674,9 +674,12 @@ async def event_importing_program_data(
         if record.get('session_description'):
             event_session_data['description'] = record.get('session_description', '').strip()
 
+        if 'session_start_datetime' in record:
             event_session_data['start_datetime'] = _clean_datetime(record.get('session_start_datetime'))
+        if 'session_end_datetime' in record:
             event_session_data['end_datetime'] = _clean_datetime(record.get('session_end_datetime'))
 
+        if 'session_sort' in record:
             event_session_data['sort'] = record.get('session_sort')
 
         if record.get('hide_session') in (True, 1, 'yes', 'Yes', 'YES'):
@@ -736,30 +739,33 @@ async def event_importing_program_data(
         event_presentation_data = {}
         if record.get('presentation_code'):
             event_presentation_data['code'] = record.get('presentation_code', '').strip()
-        else:
+        elif 'presentation_code' in record:
             event_presentation_data['code'] = None
         event_presentation_data['event_id'] = event_id # INSERT and UPDATE the event_id just in case
         event_presentation_data['event_session_id'] = event_session_id # UPDATE the event_session_id in case the presentation was moved
 
         if record.get('presentation_name'):
             event_presentation_data['name'] = record.get('presentation_name', '').strip()
-        else:
+        elif 'presentation_name' in record:
             event_presentation_data['name'] = None
 
         if record.get('presentation_description'):
             event_presentation_data['description'] = record.get('presentation_description', '').strip()
 
+        if 'presentation_start_datetime' in record:
             event_presentation_data['start_datetime'] = _clean_datetime(record.get('presentation_start_datetime'))
-        data['presentation_start_datetime'] = event_presentation_data['start_datetime']
+        data['presentation_start_datetime'] = event_presentation_data.get('start_datetime')
 
+        if 'presentation_end_datetime' in record:
             event_presentation_data['end_datetime'] = _clean_datetime(record.get('presentation_end_datetime'))
-        data['presentation_end_datetime'] = event_presentation_data['end_datetime']
+        data['presentation_end_datetime'] = event_presentation_data.get('end_datetime')
 
         if record.get('presentation_abstract_code'):
             event_presentation_data['abstract_code'] = record.get('presentation_abstract_code', '').strip()
-        else:
+        elif 'presentation_abstract_code' in record:
             event_presentation_data['abstract_code'] = None
 
+        if 'presentation_sort' in record:
             event_presentation_data['sort'] = record.get('presentation_sort')
 
         event_presentation_data['enable'] = True
@@ -768,7 +774,7 @@ async def event_importing_program_data(
             event_presentation_data['notes'] = record.get('presentation_notes', '').strip()
 
         event_presentation_id = None
-        if (record.get('presentation_external_id') or record.get('presentation_code')) and record.get('presentation_name'):
+        if record.get('presentation_external_id') or record.get('presentation_code'):
             if event_presentation_rec_result := sql_select(data=data, sql=sql):
                 # Pull out IDs and UPDATE existing event_presentation record
                 event_presentation_rec = event_presentation_rec_result
@@ -787,7 +793,7 @@ async def event_importing_program_data(
                     else:
                         log.warning(event_presentation_obj_up_result)
                         pass # Probably nothing to update
-            else:
+            elif record.get('presentation_name'):
                 log.info(f'No record found that needs to be updated. Creating a new event presentation. Event Presentation External ID: {event_presentation_external_id}')
 
                 event_presentation_data['external_id'] = event_presentation_external_id # NOTE: This should never change
@@ -868,13 +874,14 @@ async def event_importing_program_data(
             event_presenter_data['professional_title'] = record.get('presenter_professional_title', '').strip()
             event_presenter_data['affiliations'] = record.get('presenter_affiliations', '').strip()
 
+            if 'presenter_email' in record:
                 event_presenter_data['email'] = record.get('presenter_email', '').strip()
 
             event_presenter_data['enable'] = True
             event_presenter_data['notes'] = record.get('presenter_notes', '').strip()
 
             event_presenter_id = None
-            if (record.get('presenter_code') or record.get('presenter_number')) and record.get('presenter_given_name'):
+            if event_presenter_external_id:
                 if event_presenter_rec_result := sql_select(data=data, sql=sql):
                     # Pull out IDs and UPDATE existing event_presenter record
                     event_presenter_rec = event_presenter_rec_result
@@ -893,7 +900,9 @@ async def event_importing_program_data(
                         else:
                             log.warning(event_presenter_obj_up_result)
                             pass # Probably nothing to update
-                else:
+                elif (record.get('presenter_code') or record.get('presenter_number')) and record.get('presenter_given_name'):
+                    # Only INSERT when a real identifier (code/number) is available — prevents duplicates
+                    # when external_id was derived from names and lookup missed a code-keyed existing record.
                     log.info(f'No record found that needs to be updated. Creating a new event presenter. Event Presenter External ID: {event_presenter_external_id}')
 
                     event_presenter_data['external_id'] = event_presenter_external_id # NOTE: This should never change