[asgi] Headers with special characters cause the request to fail

Hi, I noticed some alerts pouring in on Sentry while setting up OpenTelemetry integration.

<details>
<summary>
TL;DR:
</summary>
A FastAPI instrumented app will throw an error with the following request:

```bash
curl 'http://localhost:1234' -H $'X-Custom-Header: \xe9'
```
</details>

I dug deeper and found that this issue does not exist in the Flask instrumentation. Werkzeug's implementation uses [`http.client.parse_headers`](https://docs.python.org/3/library/http.client.html#http.client.parse_headers) which has already decoded headers as `iso-8859-1` before being passed to the instrumentor. Meanwhile, the ASGI instrumentor receives headers as bytes and incorrectly tires to decode headers as `utf-8` which causes this error.

**Describe your environment** 

Python version: 3.10.10
OS: Manjaro

**Steps to reproduce**

### `server.py`

<details>
<summary>
server.py
</summary>

```python
import uvicorn
from fastapi import FastAPI
from opentelemetry.instrumentation.fastapi import FastAPIInstrumentor
from opentelemetry.trace import (
    set_tracer_provider,
)
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import (
    SimpleSpanProcessor,
    ConsoleSpanExporter,
)

provider = TracerProvider()
provider.add_span_processor(SimpleSpanProcessor(ConsoleSpanExporter()))
set_tracer_provider(provider)


app = FastAPI()

FastAPIInstrumentor.instrument_app(app)


@app.get("/")
def read_root():
    return {"Hello": "World"}


if __name__ == "__main__":
    uvicorn.run(app, host="localhost", port=1234)
```
</details>

### `client.py`

<details>
<summary>
client.py
</summary>

```python
import requests
requests.get('http://localhost:1234', headers={'custom-header': 'é'}).text
```
</details>

Curl equivalent: `curl 'http://localhost:1234' -H $'X-Custom-Header: \xe9'`



**What is the expected behavior?**

Client side input shouldn't cause the request to fail.

**What is the actual behavior?**

Request fails with "Internal Server Error"

<details>
<summary>
Traceback
</summary>

```
Traceback (most recent call last):
  File "/home/gagan/.virtualenvs/otel/lib/python3.10/site-packages/opentelemetry/instrumentation/asgi/__init__.py", line 539, in __call__
    custom_attributes = collect_custom_request_headers_attributes(
  File "/home/gagan/.virtualenvs/otel/lib/python3.10/site-packages/opentelemetry/instrumentation/asgi/__init__.py", line 342, in collect_custom_request_headers_attributes
    headers = {
  File "/home/gagan/.virtualenvs/otel/lib/python3.10/site-packages/opentelemetry/instrumentation/asgi/__init__.py", line 343, in <dictcomp>
    _key.decode("utf8"): _value.decode("utf8")
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe9 in position 0: unexpected end of data

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/gagan/.virtualenvs/otel/lib/python3.10/site-packages/uvicorn/protocols/http/h11_impl.py", line 428, in run_asgi
    result = await app(  # type: ignore[func-returns-value]
  File "/home/gagan/.virtualenvs/otel/lib/python3.10/site-packages/uvicorn/middleware/proxy_headers.py", line 78, in __call__
    return await self.app(scope, receive, send)
  File "/home/gagan/.virtualenvs/otel/lib/python3.10/site-packages/fastapi/applications.py", line 276, in __call__
    await super().__call__(scope, receive, send)
  File "/home/gagan/.virtualenvs/otel/lib/python3.10/site-packages/starlette/applications.py", line 122, in __call__
    await self.middleware_stack(scope, receive, send)
  File "/home/gagan/.virtualenvs/otel/lib/python3.10/site-packages/starlette/middleware/errors.py", line 184, in __call__
    raise exc
  File "/home/gagan/.virtualenvs/otel/lib/python3.10/site-packages/starlette/middleware/errors.py", line 162, in __call__
    await self.app(scope, receive, _send)
  File "/home/gagan/.virtualenvs/otel/lib/python3.10/site-packages/opentelemetry/instrumentation/asgi/__init__.py", line 565, in __call__
    duration = max(round((default_timer() - start) * 1000), 0)
UnboundLocalError: local variable 'start' referenced before assignment
```
</details>

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

[asgi] Headers with special characters cause the request to fail #1814

`server.py`

`client.py`

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

[asgi] Headers with special characters cause the request to fail #1814

Description

server.py

client.py

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions

`server.py`

`client.py`