feat(rust): explicitly derive Message trait

[Szymongib]

Current Behaviour

Currently Message trait is implicitly derived for all types that implement Serialize and DeserializeOwned traits.

Proposed Changes

Require explicit derive of Message trait for custom types for additional type safety guarantee when sending messages.

Fixes: #1849

Checks

• All commits in this Pull Request are signed.
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• I accept the Ockam Community Code of Conduct.
• I have accepted the Ockam Contributor Licence Agreement by adding my Git/Github details in a row at the end of the CONTRIBUTORS.csv file in a separate pull request to the ockam-network/contributors repository. - PR https://github.com/ockam-network/contributors/pull/48

[mrinalwadhwa]

This should be a relative link to the ockam license file instead of a copy of the license.

[mrinalwadhwa]

Thank you for sending the PR ❤️

Before we can merge, please:

• Accept the Ockam Contributor Licence Agreement by adding my Git/Github details in a row at the end of the CONTRIBUTORS.csv file in a separate pull request to the ockam-network/contributors repository.

Looking forward to merging your first contribution!!

[jdspdx]

Thanks for your contribution! I've rebased and merged these commits in #2137