Echo CTI connector

[firatesatoglu]

Proposed changes

• Add new external import connector for Echo CTI threat intelligence platform
• Fetches IOCs (IP, URL, Hash, IP-Range) from Echo CTI API
• Converts data to STIX 2.1 format and imports to OpenCTI

Related issues

• N/A (new connector)

Checklist

• I consider the submitted work as finished
• I have signed my commits using GPG key.
• I tested the code for its functionality using different use cases
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments

This connector integrates Echo CTI threat intelligence platform with OpenCTI.
It supports filtering by IOC type, state, time range, vendor, and tags.

[romain-filigran]

Hey @firatesatoglu. To be able to merge your contribution, can you please fix the name of the logo file and resolve the various linter issues ?

[romain-filigran]

Could you rename the file to "logo.png"