DDS: Cisco Secure Email Threat Defense: Crawler Integration without Assets

[ankitarajput-crest]

What does this PR do?

PR includes skeleton of Cisco Secure Email Threat Defense integration without any assets like dashboards, image, README content, etc.

Motivation

This is beta release of crawler integration and is intended for internal testing before going live. As per @nathanmadams's suggestion, we are planning to raise separate PR with assets and all necessary information later.

Additional Notes

Only crawler-based integration related changes are included in this PR.

Review checklist (to be filled by reviewers)

• [ ] Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• [ ] Changelog entries must be created for modifications to shipped code
• [ ] Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• [ ] If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[ankitarajput-crest]

@Wyrine Previously for Cisco Secure Endpoint, we have received comment to to keep source_type_name as natural title-cased. Can you please let us know which one to keep?

natural title-cased is correct. Apologies for the confusion. Please fix merge conflicts and then I will approve

@Wyrine Have fixed merge conflicts.