Downgrade rule version before uploading to Kibana

[rw-access]

Issues

Closes #96

Summary

Now that #84 is done, we can connect all the pieces together for kibana-upload.
Now, kibana-upload can work for 7.8 and 7.8 stacks. If we were to extend support further back, we just need to update schemas/v77.py accordingly.

There are still some other things to figure out for a bigger picture repository <--> Kibana workflow. But for now, this helps with the ad-hoc upload command.

Stdout

On error message (hard coded 7.7)

...
  File "/Users/rwolf/Development/detection-rules/detection_rules/eswrap.py", line 256, in kibana_upload
    payload = downgrade(payload, "7.7.0")
  File "/Users/rwolf/Development/detection-rules/detection_rules/schemas/__init__.py", line 40, in downgrade
    raise ValueError(f"Unable to downgrade from {CurrentSchema.STACK_VERSION} to {target_version_str}")
ValueError: Unable to downgrade from 7.9 to 7.7.0

On success

$ python -m detection_rules kibana-upload rules/aws/impact_iam_group_deletion.toml

█▀▀▄ ▄▄▄ ▄▄▄ ▄▄▄ ▄▄▄ ▄▄▄ ▄▄▄ ▄▄▄ ▄   ▄      █▀▀▄ ▄  ▄ ▄   ▄▄▄ ▄▄▄
█  █ █▄▄  █  █▄▄ █    █   █  █ █ █▀▄ █      █▄▄▀ █  █ █   █▄▄ █▄▄
█▄▄▀ █▄▄  █  █▄▄ █▄▄  █  ▄█▄ █▄█ █ ▀▄█      █ ▀▄ █▄▄█ █▄▄ █▄▄ ▄▄█

Loading rules from detection-rules/rules
Loaded 1 rules
Successfully uploaded 1 rules

[brokensound77]

This LGTM 👍 - with the 1 suggestion

This also still won't address rules from older schemas going to newer stacks where required fields may be missing, but this rolls into the bigger workflows you alluded to (can leverage rule.build to prompt for missing values) and can be addressed in a future PR

[brokensound77]

can you update line 185 to siem