* add basic telemetry features
* change pipeline_config to _component_config
* Update Documentation & Code Style
* add super().__init__() calls to error classes
* make posthog mock work with python 3.7
* Update Documentation & Code Style
* update link to docs web page
* log exceptions, send event for raised HaystackErrors, refactor Path(CONFIG_PATH)
* add comment on send_event in BaseComponent.init() and fix mypy
* mock NonPrivateParameters and fix pylint undefined-variable
* Update Documentation & Code Style
* check model path contains multiple /
* add test for writing to file
* add test for en-/disable telemetry
* Update Documentation & Code Style
* merge file deletion methods and ignore pylint global statement
* Update Documentation & Code Style
* set env variable in demo to activate telemetry
* fix mock of HAYSTACK_TELEMETRY_ENABLED
* fix mypy and linter
* add CI as env variable to execution contexts
* remove threading, add test for custom error event
* Update Documentation & Code Style
* simplify config/log file deletion
* add test for final event being sent
* force writing config file in test
* make test compatible with python 3.7
* switch to posthog production server
* Update Documentation & Code Style
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