enhance(tracing): customizable tasks sampler

[plyr4]

support for customizing the tracing sampler on a per-task basis.

{
    "task-name": {
        "active": bool
    }
}

a task is basically the "span name" based on the work being performed.
a task can be an API endpoint interaction, a gorm query, etc. see: https://opentelemetry.io/docs/specs/otel/trace/api/#span

if a task is not represented in the configuration file then the task will be treated normally, with tracing enabled.

consider the following example configuration files:

Example 1

this will enable all tracing.

{}

Example 2

this will enable all tracing except for the /health endpoint.

{
    "/health": {
        "active": false
    }
}

Example 3

{
    "/health": {
        "active": false
    },
    "/api/v1/deployments/:org/:repo": {
        "active": false
    },
    "/api/v1/:worker": {
        "active": true
    },
    "gorm.query": {
        "active": false
    }
}

/health with active: false will disable tracing on /health.

/api/v1/deployments/:org/:repo with active: false will disable tracing on /api/v1/deployments/:org/:repo for ALL :org and :repo parameters.

/api/v1/:worker with active: true will do nothing at this point, because any tasks that are not present in the configuration file will automatically be sampled normally.
for now this is slightly confusing, but in the future there will be more configuration fields that will determine how an active: true task is sampled.

gorm.query with active: false would disable tracing for raw gorm queries. this is meant to show that the config applies to all trace tasks and not just API/HTTP endpoints.

all other tasks will be sampled as normal using the parent rate limit sampler! this includes all api endpoints and gorm queries.

Potential Enhancements

planning future enhancements like per-task ratio-sampling and per-endpoint method restrictions.

consider the following stretch goal configuration file:

{
    "/health": {
        "active": false
    },
    "/api/v1/deployments/:org/:repo": {
        "active": true,
        "ratio": 0.3, // record only 30% 
        "methods": [ "get", "put" ], // record particular methods
        "query_parameters": [ "event=push" ] // record particular queries
    },

[codecov]

Codecov Report

Attention: Patch coverage is 38.88889% with 11 lines in your changes missing coverage. Please review.

Project coverage is 53.05%. Comparing base (ddee444) to head (bc7cdf3).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
tracing/config.go	0.00%	9 Missing ⚠️
tracing/sampler.go	77.77%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1184      +/-   ##
==========================================
- Coverage   53.06%   53.05%   -0.02%     
==========================================
  Files         559      559              
  Lines       19722    19740      +18     
==========================================
+ Hits        10466    10473       +7     
- Misses       8688     8699      +11     
  Partials      568      568              

Files with missing lines	Coverage Δ
tracing/sampler.go	21.87% <77.77%> (+21.87%)	⬆️
tracing/config.go	0.00% <0.00%> (ø)