chore: prepare release 1.21.0/0.48.0

[pichlermarc]

1.21.0

🚀 (Enhancement)

• feat(sdk-metrics): add constructor option to add metric readers #4427 @pichlermarc
  • deprecates MeterProvider.addMetricReader() please use the constructor option readers instead.

🐛 (Bug Fix)

• fix(sdk-trace-base): ensure attribute value length limit is enforced on span creation #4417 @pichlermarc
• fix(sdk-trace-base): Export processed spans while exporter failed #4287 @Zirak

🏠 (Internal)

• chore(opentelemetry-context-zone-peer-dep): support zone.js ^v0.13.0 #4320
• refactor(core): drop unnecessary assignment of HOSTNAME #4421 @pichlermarc
• test(opentelemetry-context-zone-peer-dep): transpile zone.js in tests #4423 @legendecas

Experimental 0.48.0

💥 Breaking Change

• fix(instrumentation)!: pin import-in-the-middle@1.7.1 #4441
  • Fixes a bug where, in some circumstances, ESM instrumentation packages would try to instrument CJS exports on ESM, causing the end-user application to crash.
  • This breaking change only affects users that are using the experimental @opentelemetry/instrumentation/hook.mjs loader hook AND Node.js 18.19 or later:
    • This reverts back to an older version of import-in-the-middle due to @@toStringTag property not present on modules passed to hookFn  nodejs/import-in-the-middle#57
    • This version does not support Node.js 18.19 or later

🐛 (Bug Fix)

• fix(exporter-prometheus): avoid invoking callback synchronously #4431 @legendecas
• fix(exporter-logs-otlp-grpc): set User-Agent header #4398 @Vunovati
• fix(exporter-logs-otlp-http): set User-Agent header #4398 @Vunovati
• fix(exporter-logs-otlp-proto): set User-Agent header #4398 @Vunovati
• fix(instrumentation-fetch): compatibility with Map types for fetch headers

🏠 (Internal)

• refactor(exporter-prometheus): promisify prometheus tests #4431 @legendecas

[codecov]

Codecov Report

Merging #4442 (f118581) into main (3711990) will increase coverage by 0.22%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4442      +/-   ##
==========================================
+ Coverage   92.00%   92.23%   +0.22%     
==========================================
  Files         329      336       +7     
  Lines        9093     9525     +432     
  Branches     1936     2020      +84     
==========================================
+ Hits         8366     8785     +419     
- Misses        727      740      +13     

see 7 files with indirect coverage changes

[pksunkara]

@pichlermarc I am curious, why was api package not released?

[pichlermarc]

@pichlermarc I am curious, why was api package not released?

We were mainly interested in releasing #4441 which is blocking browser users from using OTel without a path polyfill. The next feature release will be made alongside an API release.