Simplify code for JSON audit log

[JakubOnderka]

yajl_gen_string doesn't require null terminated string, so we don't need to call strlen.

This simplifies code for JSON transaction logging.

[airween]

Hi @JakubOnderka,

thanks for this PR!

Have you seen the issue #3310? There the OP mentioned a commit - may be we can consider to add that modification too. What do you think?

[JakubOnderka]

Good question. So I added test case that verifies if timestamp is correct in JSON format and it looks good.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[JakubOnderka]

@airween I also find out that in some cases, JSON log is invalid because m_httpVersion variable is empty string. So I converted http_version field in JSON audit log to string, so if m_httpVersion will be empty, JSON will still be valid.

[airween]

LGTM

[airween]

Hi @JakubOnderka,

a nice catch again - thank you!