local connector metadata and deserialization fix (#1800)
### Description
* Priority of this was to fix deserialization of ingest docs. Currently
the source metadata wasn't being persisted
* To help debug this, source metadata was added to the local ingest doc
as well.
* Unit test added to make sure the metadata itself was persisted.
* As part of serialization, it was forcing docs to fetch source metadata
if it hadn't already to add to the generated dict/json. This shouldn't
have happened if the underlying variable `_source_metadata` was `None`.
This way the doc can be serialized without any calls being made.
* Serialization was moved to the `to_dict` method to make it more
universal.
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Co-authored-by: ryannikolaidis <1208590+ryannikolaidis@users.noreply.github.com>
Co-authored-by: rbiseck3 <rbiseck3@users.noreply.github.com>
