Add check_credentials method to PostmarkEmailSender

[Copilot]

Adds validation utility for Postmark SMTP credentials used in test suite.

Changes

• PostmarkEmailSender.check_credentials(test_connection=True): Returns dict with credential status (api_token_set, sender_email_set, credentials_set) and optional SMTP connection validation (connection_valid, error)
• Tests: Added test_check_credentials_without_connection_test and test_check_credentials_with_connection_test
• Documentation: Fixed POSTMARK_API_KEY → POSTMARK_API_TOKEN env var name; added usage examples

Usage

from tests.email_sender import PostmarkEmailSender

sender = PostmarkEmailSender()

# Check credentials without testing connection
result = sender.check_credentials(test_connection=False)
# {'credentials_set': True, 'api_token_set': True, 'sender_email_set': True, 
#  'connection_valid': None, 'error': None}

# Validate credentials with SMTP connection test
result = sender.check_credentials(test_connection=True)
if result['connection_valid']:
    print("Credentials valid")
else:
    print(f"Failed: {result['error']}")

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• smtp.postmarkapp.com
  • Triggering command: `/usr/bin/python3 python3 -c
    from tests.email_sender import PostmarkEmailSender

sender = PostmarkEmailSender()

Test without connection

result = sender.check_credentials(test_connection=False)
print('Without connection test:', result)

Test with connection

result = sender.check l` (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

Crwate a new action to check if the postmark informations are set and usable

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