Deprecate Jaeger propagator (#4827)

Fixes #4786

## Changes

Deprecate Jaeger propagator and make the implementation optional.
It was already deprecated by the Jaeger team:
https://www.jaegertracing.io/sdk-migration/#propagation-format

* [x] Related issues #4786
* ~~[ ] Related [OTEP(s)](https://github.com/open-telemetry/oteps) #~~
* ~~[ ] Links to the prototypes (when adding or changing features)~~
* [x]
[`CHANGELOG.md`](https://github.com/open-telemetry/opentelemetry-specification/blob/main/CHANGELOG.md)
file updated for non-trivial changes
* For trivial changes, include `[chore]` in the PR title to skip the
changelog check
* [x] [Spec compliance
matrix](https://github.com/open-telemetry/opentelemetry-specification/blob/main/spec-compliance-matrix/template.yaml)
updated if necessary

---------

Co-authored-by: Robert Pająk <pellared@hotmail.com>

Author: Kielek

CHANGELOG.md

@@ -9,6 +9,9 @@ release.
 
 ### Context
 
+- Deprecate Jaeger propagator and make propagator implementation optional.
+  ([#4827](https://github.com/open-telemetry/opentelemetry-specification/pull/4827))
+
 ### Traces
 
 ### Metrics

spec-compliance-matrix.md

@@ -239,7 +239,7 @@ Disclaimer: this list of features is still a work in progress, please refer to t
 | Global Propagator |  | + | + | + | + | + | + | + | + | + | + | + |
 | TraceContext Propagator |  | + | + | + | + | + | + | + | + | + | + | + |
 | B3 Propagator |  | + | + | + | + | + | + | + | + | + | + | + |
-| Jaeger Propagator |  | + | + | + | + | + | + | + | + | + | - | + |
+| Jaeger Propagator | X | + | + | + | + | + | + | + | + | + | - | + |
 | OT Propagator |  | + | + | + | + |  |  |  |  |  |  |  |
 | OpenCensus Binary Propagator |  | + |  |  |  |  |  |  |  |  |  |  |
 | [TextMapPropagator](specification/context/api-propagators.md#textmap-propagator) |  | + | + |  | + | + |  | + |  | + |  |  |

spec-compliance-matrix/template.yaml

@@ -273,6 +273,7 @@ sections:
       - name: TraceContext Propagator
       - name: B3 Propagator
       - name: Jaeger Propagator
+        optional: true
       - name: OT Propagator
       - name: OpenCensus Binary Propagator
       - name: '[TextMapPropagator](specification/context/api-propagators.md#textmap-propagator)'

specification/configuration/sdk-environment-variables.md

@@ -125,7 +125,7 @@ Known values for `OTEL_PROPAGATORS` are:
 - `"baggage"`: [W3C Baggage](https://www.w3.org/TR/baggage/)
 - `"b3"`: [B3 Single](../context/api-propagators.md#configuration)
 - `"b3multi"`: [B3 Multi](../context/api-propagators.md#configuration)
-- `"jaeger"`: [Jaeger](https://www.jaegertracing.io/sdk-migration/#propagation-format)
+- `"jaeger"`: [Jaeger](https://www.jaegertracing.io/sdk-migration/#propagation-format) - **Status**: [Deprecated](../document-status.md)
 - `"xray"`: [AWS X-Ray](https://docs.aws.amazon.com/xray/latest/devguide/xray-concepts.html#xray-concepts-tracingheader) (_third party_)
 - `"ottrace"`: [OT Trace](https://github.com/opentracing?q=basic&type=&language=) (_third party_)
 - `"none"`: No automatically configured propagator.

specification/context/api-propagators.md

@@ -1,6 +1,6 @@
 # Propagators API
 
-**Status**: [Stable](../document-status.md)
+**Status**: [Stable](../document-status.md) except where otherwise specified
 
 <details>
 <summary>Table of Contents</summary>
@@ -215,8 +215,8 @@ Required arguments:
 The `Keys` function can be called by `Propagator`s which are using variable key names in order to
 iterate over all the keys in the specified carrier.
 
-For example, it can be used to detect all keys following the `uberctx-{user-defined-key}` pattern, as defined by the
-[Jaeger Propagation Format](https://www.jaegertracing.io/docs/1.76/architecture/#baggage).
+For example, it can be used to detect all keys following the `X-B3-${name}` pattern, as defined by the
+[B3 Propagation: Multiple Headers](https://github.com/openzipkin/b3-propagation/blob/master/README.md#multiple-headers).
 
 ##### Get
 
@@ -357,11 +357,13 @@ organization and MUST be distributed as OpenTelemetry extension packages:
 * [W3C Baggage](https://www.w3.org/TR/baggage/). MAY alternatively
   be distributed as part of the OpenTelemetry API.
 * [B3](https://github.com/openzipkin/b3-propagation).
-* [Jaeger](https://www.jaegertracing.io/sdk-migration/#propagation-format).
 
 This is a list of additional propagators that MAY be maintained and distributed
 as OpenTelemetry extension packages:
 
+* [Jaeger](https://www.jaegertracing.io/sdk-migration/#propagation-format).
+  **Status**: [Deprecated](../document-status.md), use the
+  [W3C TraceContext](https://www.w3.org/TR/trace-context/) instead.
 * [OT Trace](https://github.com/opentracing?q=basic&type=&language=). Propagation format
   used by the OpenTracing Basic Tracers. It MUST NOT use `OpenTracing` in the resulting
   propagator name as it is not widely adopted format in the OpenTracing ecosystem.