#837, option A

[kubukoz]

Closes #837.

• check if the protocol is already included (any version of it), before attempting to add our own from the local classpath.

Main problem: in case a lower version is included in the dependencies, the lower version will be picked for model loading - smithy4s's own fixes won't be taken into account, this could pose problems.

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PR Checklist (not all items are relevant to all PRs)

• Added unit-tests (for runtime code)
• Added bootstrapped code + smoke tests (when the rendering logic is modified)
• Added build-plugins integration tests (when reflection loading is required at codegen-time)
• Added alloy compliance tests (when simpleRestJson protocol behaviour is expanded/updated)
• Updated dynamic module to match generated-code behaviour
• Added documentation
• Updated changelog

[kubukoz]

decided to go with option B #1672