add dshield observable analyzer

[standa4]

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Description

New observable analyzer for https://isc.sans.edu (https://isc.sans.edu/ipinfo/) service.

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality).

Checklist

• I have read and understood the rules about how to Contribute to this project
• The pull request is for the branch develop
• A new plugin (analyzer, connector, visualizer, playbook, pivot or ingestor) was added or changed, in which case:
  • I strictly followed the documentation "How to create a Plugin"
  • Usage file was updated.
  • Advanced-Usage was updated (in case the plugin provides additional optional configuration).
  • I have dumped the configuration from Django Admin using the dumpplugin command and added it in the project as a data migration. ("How to share a plugin with the community")
  • If a File analyzer was added and it supports a mimetype which is not already supported, you added a sample of that type inside the archive test_files.zip and you added the default tests for that mimetype in test_classes.py.
  • If you created a new analyzer and it is free (does not require any API key), please add it in the FREE_TO_USE_ANALYZERS playbook by following this guide.
  • Check if it could make sense to add that analyzer/connector to other freely available playbooks.
  • I have provided the resulting raw JSON of a finished analysis and a screenshot of the results.
  • If the plugin interacts with an external service, I have created an attribute called precisely url that contains this information. This is required for Health Checks.
  • If the plugin requires mocked testing, _monkeypatch() was used in its class to apply the necessary decorators.
  • I have added that raw JSON sample to the MockUpResponse of the _monkeypatch() method. This serves us to provide a valid sample for testing.
• If external libraries/packages with restrictive licenses were used, they were added in the Legal Notice section.
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• I have added tests for the feature/bug I solved (see tests folder). All the tests (new and old ones) gave 0 errors.
• If changes were made to an existing model/serializer/view, the docs were updated and regenerated (check CONTRIBUTE.md).
• If the GUI has been modified:
  • I have a provided a screenshot of the result in the PR.
  • I have created new frontend tests for the new component or updated existing ones.
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Important Rules

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[mlodic]

thank you Stanislav, we'll help you finish this PR!