feat(ena-submission): Trigger ena submission

[anna-parker]

resolves #2403

preview URL: https://trigger-ena-submission.loculus.org/

Summary

1. Get sequences that have been approved for release from https://github.com/pathoplexus/ena-submission/blob/main/approved/approved_ena_submission_list.json and add them to the submission_table (if not already there), this will trigger the ena submission process.
2. Add a cronjob that calls get_ena_submission_list every day, sending a slack message with sequences that are ready for ena submission but need manual approval. (added in feat(ena-submission): Add ena slack notifications #2396)

Screenshot

PR Checklist

• feat(ena-submission): Add ena slack notifications #2396 is approved and submitted
• Generate PAT and add to secrets
• Test works locally
• Connect to DB in preview instance and check this works
  Promising logs:
  
  Connect to preview db with port forwarding (see Configure sequence approval and test we can manually trigger submission to ENA #2403 for details):

• Confirm cronjobs are working, changed cronjob to run every 15minutes (e.g. change from "0 0 * * *" to */15 * * * *) and then uploaded new sequences to the preview instance, slack notifications from the cron job are working as intended:
  - additionally they are added in a loop

[theosanderson]

lgtm