(Don't?) rename HTTPText to TextMap Propagator

[fbogsany]

open-telemetry/opentelemetry-specification#793 renamed the HttpTextPropagator to TextMapPropagator. We have a split in our implementation between http and text propagation

opentelemetry-ruby/api/lib/opentelemetry/context/propagation/propagation.rb

Lines 12 to 19 in 7a10db9

	class Propagation
	# Get or set the global http propagator. Use a CompositePropagator
	# to propagate multiple formats.
	attr_accessor :http
	# Get or set the global text propagator. Use a CompositePropagator
	# to propagate multiple formats.
	attr_accessor :text

opentelemetry-ruby/sdk/lib/opentelemetry/sdk/configurator.rb

Lines 130 to 135 in 7a10db9

	def configure_propagation
	OpenTelemetry.propagation.http = create_propagator(@http_injectors || default_http_injectors,
	@http_extractors || default_http_extractors)
	OpenTelemetry.propagation.text = create_propagator(@text_injectors || default_text_injectors,
	@text_extractors || default_text_extractors)
	end

because we need to support Rack extractors for HTTP:

opentelemetry-ruby/sdk/lib/opentelemetry/sdk/configurator.rb

Lines 149 to 154 in 7a10db9

	def default_http_extractors
	[
	OpenTelemetry::Trace::Propagation::TraceContext.rack_extractor,
	OpenTelemetry::CorrelationContext::Propagation.rack_extractor
	]
	end

vs

opentelemetry-ruby/sdk/lib/opentelemetry/sdk/configurator.rb

Lines 163 to 168 in 7a10db9

	def default_text_extractors
	[
	OpenTelemetry::Trace::Propagation::TraceContext.text_extractor,
	OpenTelemetry::CorrelationContext::Propagation.text_extractor
	]
	end

I don't think we should change anything in our implementation, since the Ruby HTTP ecosystem really requires this distinction (almost?) everywhere. I'm just creating this issue to solicit and record agreement.

cc @mwear

[mwear]

I agree it's useful to have http and text versions of the propagators readily available due to Rack. I'm wondering if we could "meet in the middle" by calling our TextInjector / Extractor a TextMapInjector / Extractor. We could keep the http and text distinction, but the types would line up with the spec. I'm also fine with keeping things as-is.

[fbogsany]

I'm wondering if we could "meet in the middle" by calling our TextInjector / Extractor a TextMapInjector / Extractor

👍 sounds good to me -- I'll PR that, perhaps tomorrow.