OTLPSpanExporter headers argument is tightly coupled to specific types

[PeterJCLaw-mns]

Describe your environment

Python 3.11, opentelemetry-exporter-otlp-proto-grpc 1.16.0

Steps to reproduce

According to the type annotations, the following code should work:

from opentelemetry.exporter.otlp.proto.grpc.trace_exporter import OTLPSpanExporter

OTLPSpanExporter(headers=[
    ('api-key': 'blah'),
])

however it results in:

TypeError: can only concatenate list (not "tuple") to list

Additionally the type signature for OTLPSpanExporter does not appear to allow passing e.g: a mapping of key value pairs to the headers, however that is in fact supported by the OTLPExporterMixin which handles the passed value.

[srikanthccv]

• Update the {span,metric,log} exporter types to match the mixin type
• Fix concatenate issue here

[sreejitkar]

Hi , I am interested in picking up this issue. This is going to be my first contribution towards OTEL so please bear with me if this takes some time. Thanks !