Upgrade Kotlin, dependencies and Dokka

[kpavlov]

• kotlin & dokka @1.5.31
• commons-lang3@3.12.0
• assertj@3.21.0
• junit@5.8.1
• mockito@3.12.4
• spring@5.3.10
• netty@4.1.68.Final
• awaitility@4.1.0

[codeclimate[bot]]

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