fix: logging service RPC json serialization

[Dogacel]

Motivation:

Explain why you're making this change and what problem you're trying to solve.

Modifications:

• List the modifications you've made in detail.

Result:

• Closes #. (If this resolves the issue.)
• Describe the consequences that a user will face after this PR is merged.

[github-actions]

🔍 Build Scan® (commit: 7be66a3)

Job name	Status	Build Scan®
build-self-hosted-unsafe-jdk-8	❌ (failure)	https://ge.armeria.dev/s/fjwm3vrdi5fsc
build-self-hosted-unsafe-jdk-21-snapshot-blockhound	❌ (failure)	https://ge.armeria.dev/s/qytxtek5jr77e
build-self-hosted-unsafe-jdk-17-min-java-17-coverage	❌ (failure)	https://ge.armeria.dev/s/uprtdet2lmaec
build-self-hosted-unsafe-jdk-17-min-java-11	❌ (failure)	https://ge.armeria.dev/s/sf2r53p5jbium
build-self-hosted-unsafe-jdk-17-leak	❌ (failure)	https://ge.armeria.dev/s/odxl2znbf5fii
build-self-hosted-unsafe-jdk-11	❌ (failure)	https://ge.armeria.dev/s/drwgnegixguk2
build-macos-12-jdk-21	❌ (failure)	https://ge.armeria.dev/s/5kbjotk5ugm7a