v0.5.2

Docker image pushed to Docker Hub:
docker pull zodac/diurnal:0.5.2

Changes since 0.5.1:

[CI]

• [dba20ef] Updating the Checkstyle config for strict indents, and applied some other styling rules to CODE_STYLE.md
• [319574c] Prepare next version: 0.5.2

[Dashboard]

• [f97653f] Fixing potential race condition for concurrent sessions logging the same action