feat: add contextual rules

[nunomaduro]

trafficstars

TL;DR: The condition field on rules is now optional.

Actions required:

• Update the cts with the information on : #71

• On strongly typed clients, update types in query rules, as the condition field in rules is now optional

• Python test suite update

[aseure]

As confirmed by @nunomaduro, not only condition becomes optional, but also condition.anchoring, condition.pattern and condition.context.