feat: add datadog_tracing directive

[dubloom]

• Deprecation for datadog_enable / datadog_disable
• Creation of datadog_tracing on/off (which do exactly the same as datadog_enable / datadog_disable)
• Creation of multiple macro for deprecating directive (one for 1.2.0, one for 1.4.0)
• Add a new test to see if the "specialization" of datadog_tracing on/off was working

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 58.97436% with 32 lines in your changes missing coverage. Please review.

Project coverage is 69.31%. Comparing base (9440247) to head (f118dba). Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
src/datadog_context.cpp	41.02%	16 Missing and 7 partials :warning:
src/datadog_handler.cpp	71.42%	6 Missing :warning:
src/datadog_directive.cpp	76.92%	3 Missing :warning:

Additional details and impacted files

[](https://app.codecov.io/gh/DataDog/nginx-datadog/pull/124?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog) ```diff @@ Coverage Diff @@ ## master #124 +/- ## ========================================== - Coverage 77.18% 69.31% -7.88% ========================================== Files 36 36 Lines 3963 4879 +916 Branches 669 676 +7 ========================================== + Hits 3059 3382 +323 - Misses 868 1143 +275 - Partials 36 354 +318 ``` | [Files with missing lines](https://app.codecov.io/gh/DataDog/nginx-datadog/pull/124?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog) | Coverage Δ | | |---|---|---| | [src/ngx\_http\_datadog\_module.cpp](https://app.codecov.io/gh/DataDog/nginx-datadog/pull/124?src=pr&el=tree&filepath=src%2Fngx_http_datadog_module.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog#diff-c3JjL25neF9odHRwX2RhdGFkb2dfbW9kdWxlLmNwcA==) | `59.06% <100.00%> (-12.78%)` | :arrow_down: | | [src/datadog\_directive.cpp](https://app.codecov.io/gh/DataDog/nginx-datadog/pull/124?src=pr&el=tree&filepath=src%2Fdatadog_directive.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog#diff-c3JjL2RhdGFkb2dfZGlyZWN0aXZlLmNwcA==) | `53.38% <76.92%> (-1.85%)` | :arrow_down: | | [src/datadog\_handler.cpp](https://app.codecov.io/gh/DataDog/nginx-datadog/pull/124?src=pr&el=tree&filepath=src%2Fdatadog_handler.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog#diff-c3JjL2RhdGFkb2dfaGFuZGxlci5jcHA=) | `62.50% <71.42%> (-7.20%)` | :arrow_down: | | [src/datadog\_context.cpp](https://app.codecov.io/gh/DataDog/nginx-datadog/pull/124?src=pr&el=tree&filepath=src%2Fdatadog_context.cpp&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog#diff-c3JjL2RhdGFkb2dfY29udGV4dC5jcHA=) | `56.86% <41.02%> (-15.05%)` | :arrow_down: | ... and [29 files with indirect coverage changes](https://app.codecov.io/gh/DataDog/nginx-datadog/pull/124/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog)

[dubloom]

I don't know if I agree with us completely deprecating commands straight away without keeping backwards compatibility at least for a while. Or if we do, let's do it completely without showing a deprecation message that doesn't really explain how to solve the problem. We should define a strategy on how to approach deprecations

We can also create more specific deprecation function. I.e a function which will print: it is deprecated, use this new directive instead

[dubloom]

I resolve the conflicts, can you give a quick look please @pablomartinezbernardo ?