fix bad linux filename generation

currently maigret parses urls as usernames related to gravatar. this leads to bad filenames of the output on my linux host, as the slashes cause it to try to write subfolders, causing the script to abort with the error "file does not exist".
Applied a simple fix to replace all "/" with "_" in output file generation.

maigret/maigret.py

@@ -8,6 +8,7 @@
 import os
 import sys
 import platform
+import re
 from argparse import ArgumentParser, RawDescriptionHelpFormatter
 from typing import List, Tuple
 import os.path as path
@@ -679,25 +680,30 @@ async def main():
         # TODO: tests
         if recursive_search_enabled:
             extracted_ids = extract_ids_from_results(results, db)
+            query_notify.warning(f'Extracted IDs: {extracted_ids}')
             usernames.update(extracted_ids)
 
         # reporting for a one username
         if args.xmind:
+            username = username.replace('/', '_')
             filename = report_filepath_tpl.format(username=username, postfix='.xmind')
             save_xmind_report(filename, username, results)
             query_notify.warning(f'XMind report for {username} saved in {filename}')
 
         if args.csv:
+            username = username.replace('/', '_')
             filename = report_filepath_tpl.format(username=username, postfix='.csv')
             save_csv_report(filename, username, results)
             query_notify.warning(f'CSV report for {username} saved in {filename}')
 
         if args.txt:
+            username = username.replace('/', '_')
             filename = report_filepath_tpl.format(username=username, postfix='.txt')
             save_txt_report(filename, username, results)
             query_notify.warning(f'TXT report for {username} saved in {filename}')
 
         if args.json:
+            username = username.replace('/', '_')
             filename = report_filepath_tpl.format(
                 username=username, postfix=f'_{args.json}.json'
             )
@@ -715,18 +721,21 @@ async def main():
         username = report_context['username']
 
         if args.html:
+            username = username.replace('/', '_')
             filename = report_filepath_tpl.format(
                 username=username, postfix='_plain.html'
             )
             save_html_report(filename, report_context)
             query_notify.warning(f'HTML report on all usernames saved in {filename}')
 
         if args.pdf:
+            username = username.replace('/', '_')
             filename = report_filepath_tpl.format(username=username, postfix='.pdf')
             save_pdf_report(filename, report_context)
             query_notify.warning(f'PDF report on all usernames saved in {filename}')
 
         if args.graph:
+            username = username.replace('/', '_')
             filename = report_filepath_tpl.format(
                 username=username, postfix='_graph.html'
             )