[mod_logfile] Add structured channel log tags

[BIT-ja]

Description

Adds structured per-channel context to mod_logfile output and a set_log_tag dialplan application.

set_log_tag name=value sets or replaces a channel log tag. set_log_tag name= and set_log_tag name remove it. mod_logfile can include captured tags and configured live channel variables in the prefix of each physical log line.

The implementation also handles APR short writes, partial-error writes, transient reopen failures, HUP/rotation cleanup, allocation failures with raw fallback, and UTF-8-safe value sanitation.

Existing UUID behavior remains enabled by default. log-tags and channel-vars are opt-in.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Code cleanup / refactor

Related Issues

None.

Testing

Validated in a Linux amd64 ASAN container:

• make -j10

• switch_log: 4/4

• test_mod_logfile_prefix: 18/18

• test_mod_logfile: 2/2

• XML parsing and git diff --check

• Added/updated unit tests

• Tested manually

• Tested with live SignalWire credentials (if applicable)

Checklist

• I have read the CONTRIBUTING guidelines
• My code follows the project's style guidelines
• I have added tests for my changes (if applicable)
• I have updated documentation (if applicable)
• All existing tests pass

Additional Notes

Example profile settings:

<param name="uuid" value="true"/>
<param name="log-tags" value="true"/>
<param name="channel-vars" value="sip_call_id=callid,caller_id_number"/>

[timando]

I already made my own module to set log tags but it behaves a bit differently. set_log_tag name is equivalent to set_log_tag name=${name} instead of deleting the log tag. Also, I would expect set_log_tag name=_undef_ to unset the log tag.