feat(http-log): support charset in content-type header

[tysoekong]

Summary

Checklist

• The Pull Request has tests
• There's an entry in the CHANGELOG
• There is a user-facing docs PR against https://github.com/Kong/docs.konghq.com -docs(http-log): plugin schema update for 3.3 docs.konghq.com#5326

Full changelog

• adds application/json; charset=utf-8 option for the Content-Type header in the http-log plugin, for log collectors that require that character set declaration.

Issue reference

Reported in FTI 4931.

[CLAassistant]

All committers have signed the CLA.

[tysoekong]

Integration tests are failing at PDK stage:

spec/02-integration/07-sdk/05-pdk_spec.lua:54: Expected strings to match.
Passed in:
(string) '{"headers":{"connection":"keep-alive","host":"127.0.0.1:15555","user-agent":"lua-resty-http/0.17.0-beta.1 (Lua) ngx_lua/10021","x-real-ip":"127.0.0.1","x-forwarded-for":"127.0.0.1","x-forwarded-host":"test.com","x-forwarded-port":"9000","x-forwarded-path":"/request","x-forwarded-proto":"http"},"uri_args":{},"vars":{"request_time":"0.000","host":"127.0.0.1","request":"GET /request HTTP/1.1","server_protocol":"HTTP/1.1","realip_remote_addr":"127.0.0.1","remote_addr":"127.0.0.1","ssl_server_name":"no SNI","request_method":"GET","hostname":"fv-az267-679","realip_remote_port":"51262","remote_port":"","uri":"/request","is_args":"","request_uri":"/request","binary_remote_addr":"\u007f\u0000\u0000\u0001","scheme":"http","https":"","request_length":"289","server_name":"mock_upstream","server_port":"15555","server_addr":"127.0.0.1"},"post_data":{"params":null,"text":"","kind":"unknown"},"url":"http://127.0.0.1:15555/request"}'
Expected:
(string) '^%x%x%x%x%x%x%x%x%-%x%x%x%x%-%x%x%x%x%-%x%x%x%x%-%x%x%x%x%x%x%x%x%x%x%x%x$'

I do not think that I have broken this, it is a missing string substitution or something...?

[bungle]

Integration tests are failing at PDK stage:

I do not think that I have broken this, it is a missing string substitution or something...?

Yes, this is seen in other prs too.