…erver side SDK. (#2829)

* add serialization method to server side remote config

* update with latest changes

* restructure as a class, add documentation

* more tests for server config

* run apidocs

* Refine api and rerun docs

* add back the newline

* Apply suggestions from review

* Make eTag optional in fetch response

* rerun doc generator

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Co-authored-by: Kevin Elko <kjelko@google.com>