Make span attributes json parseable for celery

Describe your environment

OS: (e.g, Ubuntu)
Python version: (e.g., Python 3.8.10)
Package version: (e.g., 0.46.0)

What happened?

Currently, the "delivery_info" attribute in celery is a string and not a map (or even a json).
The attribute is transformed into a string, which makes it hard to parse, and one has to use regex instead.

Steps to Reproduce

Run the celery instrumentation application from https://github.com/shivanshuraj1333/celery-opentelemetry-instrumentation/

Expected Result

attribute name: celetry.delivery_info

option 1: return a python dict

{
    'exchange': '',
    'routing_key': 'queue2',
    'priority': 0,
    'redelivered': False
}

option 2: return a valid json

{
  "exchange": "",
  "routing_key": "queue2",
  "priority": 0,
  "redelivered": false
}

A dict is supported by semconv and proto message https://github.com/open-telemetry/opentelemetry-proto/blob/main/opentelemetry/proto/common/v1/common.proto#L37

Also, the unmarshalling is already supported, see.

So, let's go for having option 1 makes sense, since, it helps in extracting the keys from map values of an attribute

Actual Result

attribute name: celetry.delivery_info
value: {'exchange': '', 'routing_key': 'queue2', 'priority': 0, 'redelivered': False}

Additional context

No response

Would you like to implement a fix?

None

Start with the Celery instrumentation application linked in the reproduction steps and trace where the delivery_info span attribute is created. Compare its current value with the OpenTelemetry common.proto attribute map and the exporter unmarshalling code linked in the issue; done means delivery_info is emitted as a map that preserves its keys and value types.