Delete a baggage item when value is blank

[zacscoding]

Which problem is this PR solving?

• delete a baggage item in span if provided empty value.

Short description of the changes

• if sets to blank values in span context, then delete a baggage item.

[codecov]

Codecov Report

Merging #562 (7c867de) into master (fe3fa55) will increase coverage by 1.89%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #562      +/-   ##
==========================================
+ Coverage   88.64%   90.53%   +1.89%     
==========================================
  Files          61       24      -37     
  Lines        3311     1670    -1641     
==========================================
- Hits         2935     1512    -1423     
+ Misses        249      109     -140     
+ Partials      127       49      -78     

Impacted Files	Coverage Δ
span_context.go	94.30% <100.00%> (+0.34%)	⬆️
testutils/udp_transport.go
internal/baggage/remote/restriction_manager.go
testutils/sampling_manager.go
rpcmetrics/metrics.go
log/zap/logger.go
utils/reconnecting_udp_conn.go
internal/baggage/remote/options.go
utils/udp_client.go
transport/http.go
... and 28 more

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[yurishkuro]

please make sure all commits are signed (see CONTRIBUTING)

[yurishkuro]

Suggested change

	if _, ok := c.baggage[key]; ok {
	newBaggage = make(map[string]string, len(c.baggage))
	for k, v := range c.baggage {
	newBaggage[k] = v
	}
	delete(newBaggage, key)
	} else {
	newBaggage = c.baggage
	}
	return SpanContext{c.traceID, c.spanID, c.parentID, newBaggage, "", c.samplingState, c.remote}
	if _, ok := c.baggage[key]; !ok {
	return c
	}
	newBaggage = make(map[string]string, len(c.baggage))
	for k, v := range c.baggage {
	newBaggage[k] = v
	}
	delete(newBaggage, key)
	return SpanContext{c.traceID, c.spanID, c.parentID, newBaggage, "", c.samplingState, c.remote}

[yurishkuro]

Suggested change

	assert.Equal(t, map[string]string{"some-KEY": "Some-Value"}, ctx.baggage)
	assert.Equal(t, map[string]string{"some-KEY": "Some-Value"}, ctx.baggage)
	ctx = ctx.WithBaggageItem("another-KEY", "")
	assert.Equal(t, map[string]string{"some-KEY": "Some-Value"}, ctx.baggage)

[yurishkuro]

Suggested change

	ctx = ctx.WithBaggageItem("some-KEY", "")
	assert.Equal(t, map[string]string{}, ctx.baggage)
	ctx2 := ctx.WithBaggageItem("some-KEY", "")
	assert.Equal(t, map[string]string{"some-KEY": "Some-Value"}, ctx.baggage, "parent unchanged")
	assert.Equal(t, map[string]string{}, ctx2.baggage)

[zacscoding]

@yurishkuro thx for review :) updated all comments 👍