Adds union operator in the or clause

[rkodev]

IMPORTANT: All PRs must be linked to an issue (except for extremely trivial and straightforward changes).

Fixes #292

Description
Allows composite search by adding complex search parameters

Alternative(s) considered
N/A Currently not possible to create composite search

Type
Feature

Screenshots (if applicable)

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[jingtang10]

Thanks @rkodev! Can you please write down what the new search API would look like with this change?

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