Clarify key-value format (issue 4296)

[sparecycles]

Fixes #4296

The documentation was a little misleading (to me at least) if I focused on this part alone:

... except that additional semi-colon delimited metadata is not supported, i.e.: key1=value1,key2=value2.
as the "i.e.," was illustrating correct/supported usage and not note that immediately preceded it.

Changes

FROM

The OTEL_EXPORTER_OTLP_HEADERS, OTEL_EXPORTER_OTLP_TRACES_HEADERS, OTEL_EXPORTER_OTLP_METRICS_HEADERS, OTEL_EXPORTER_OTLP_LOGS_HEADERS environment variables will contain a list of key value pairs, and these are expected to be represented in a format matching to the W3C Baggage, except that additional semi-colon delimited metadata is not supported, i.e.: key1=value1,key2=value2. All attribute values MUST be considered strings.

TO

The OTEL_EXPORTER_OTLP_HEADERS, OTEL_EXPORTER_OTLP_TRACES_HEADERS, OTEL_EXPORTER_OTLP_METRICS_HEADERS, OTEL_EXPORTER_OTLP_LOGS_HEADERS environment variables will contain a list of key value pairs, and these are expected to be represented in a format matching W3C Baggage i.e., key1=value1,key2=value2. Semi-colon delimited metadata is not supported. All attribute values MUST be considered strings.

(strikethough and bold added here to highlight differences)

• Related issues Page feedback - exporter (delimiters) #4296
• Related OTEP(s) #
• Links to the prototypes (when adding or changing features)
• CHANGELOG.md file updated for non-trivial changes
• spec-compliance-matrix.md updated if necessary

[linux-foundation-easycla]

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[reyang]

Maybe add a link to "Semi-colon delimited metadata", point to https://www.w3.org/TR/baggage/#property.

[MrAlias]

Please be sure to sign the CLA so these changes can be evaluated.

[sparecycles]

Sorry, I don't really have the time/energy to go through the CLA process just to push trivial documentation changes (involves internal company approval processes as well).

Thanks for answering my questions, though!