Remove letters-related code (#175)

This deletes a big ol' chunk of code related to letters. It's not everything—there are still a few things that might be tied to sms/email—but it's the the heart of letters function. SMS and email function should be untouched by this.

Areas affected:

- Things obviously about letters
- PDF tasks, used for precompiling letters
- Virus scanning, used for those PDFs
- FTP, used to send letters to the printer
- Postage stuff

app/platform_stats/rest.py

@@ -7,8 +7,6 @@ from app.dao.fact_billing_dao import (
     fetch_billing_details_for_all_services,
     fetch_daily_sms_provider_volumes_for_platform,
     fetch_daily_volumes_for_platform,
-    fetch_letter_costs_and_totals_for_all_services,
-    fetch_letter_line_items_for_all_services,
     fetch_sms_billing_for_all_services,
     fetch_volumes_by_service,
 )
@@ -16,7 +14,6 @@ from app.dao.fact_notification_status_dao import (
     fetch_notification_status_totals_for_all_services,
 )
 from app.errors import InvalidRequest, register_errors
-from app.models import UK_POSTAGE_TYPES
 from app.platform_stats.platform_stats_schema import platform_stats_request
 from app.schema_validation import validate
 from app.service.statistics import format_admin_stats
@@ -75,14 +72,7 @@ def get_data_for_billing_report():
     start_date, end_date = validate_date_range_is_within_a_financial_year(start_date, end_date)
 
     sms_costs = fetch_sms_billing_for_all_services(start_date, end_date)
-    letter_overview = fetch_letter_costs_and_totals_for_all_services(start_date, end_date)
-    letter_breakdown = fetch_letter_line_items_for_all_services(start_date, end_date)
 
-    lb_by_service = [
-        (lb.service_id,
-         f"{lb.letters_sent} {postage_description(lb.postage)} letters at {format_letter_rate(lb.letter_rate)}")
-        for lb in letter_breakdown
-    ]
     combined = {}
     for s in sms_costs:
         if float(s.sms_cost) > 0:
@@ -93,34 +83,9 @@ def get_data_for_billing_report():
                 "service_name": s.service_name,
                 "sms_cost": float(s.sms_cost),
                 "sms_chargeable_units": s.chargeable_billable_sms,
-                "total_letters": 0,
-                "letter_cost": 0,
-                "letter_breakdown": ""
             }
             combined[s.service_id] = entry
 
-    for data in letter_overview:
-        if data.service_id in combined:
-            combined[data.service_id].update(
-                {'total_letters': data.total_letters, 'letter_cost': float(data.letter_cost)}
-            )
-
-        else:
-            letter_entry = {
-                "organisation_id": str(data.organisation_id) if data.organisation_id else "",
-                "organisation_name": data.organisation_name or "",
-                "service_id": str(data.service_id),
-                "service_name": data.service_name,
-                "sms_cost": 0,
-                "sms_chargeable_units": 0,
-                "total_letters": data.total_letters,
-                "letter_cost": float(data.letter_cost),
-                "letter_breakdown": ""
-            }
-            combined[data.service_id] = letter_entry
-    for service_id, breakdown in lb_by_service:
-        combined[service_id]['letter_breakdown'] += (breakdown + '\n')
-
     billing_details = fetch_billing_details_for_all_services()
     for service in billing_details:
         if service.service_id in combined:
@@ -156,8 +121,6 @@ def daily_volumes_report():
             "sms_fragment_totals": int(row.sms_fragment_totals),
             "sms_chargeable_units": int(row.sms_chargeable_units),
             "email_totals": int(row.email_totals),
-            "letter_totals": int(row.letter_totals),
-            "letter_sheet_totals": int(row.letter_sheet_totals)
         })
     return jsonify(report)
 
@@ -201,23 +164,6 @@ def volumes_by_service_report():
             "sms_notifications": int(row.sms_notifications),
             "sms_chargeable_units": int(row.sms_chargeable_units),
             "email_totals": int(row.email_totals),
-            "letter_totals": int(row.letter_totals),
-            "letter_sheet_totals": int(row.letter_sheet_totals),
-            "letter_cost": float(row.letter_cost),
         })
 
     return jsonify(report)
-
-
-def postage_description(postage):
-    if postage in UK_POSTAGE_TYPES:
-        return f'{postage} class'
-    else:
-        return 'international'
-
-
-def format_letter_rate(number):
-    if number >= 1:
-        return f"£{number:,.2f}"
-
-    return f"{number * 100:.0f}p"