fix: recognize POST method as cacheable

[99sphere]

Description

I am using fastapi-cache for my project and encountered a small issue regarding request caching. Currently, the _uncachable function allows caching only for GET requests, and I would like to propose allowing POST requests as well.

Use Case

In my setup, I use a Bastion Host to receive user requests and forward them to the actual server. To reduce unnecessary computations, I want to cache responses for POST requests when the same input is provided multiple times. There are cases where multiple identical requests are sent in a short period, and caching can help prevent redundant processing. However, since _uncachable restricts caching to GET requests, I am unable to achieve this with the current implementation.
Allowing caching for POST requests could be useful when performing idempotent operations based on the user's request.

Proposed Change

I modified the code to allow caching for POST requests and confirmed that it works correctly. If there are no other logical issues, would it be possible to consider making this behavior configurable or allowing caching for POST requests under certain conditions?

Looking forward to your thoughts. Thanks!

[JonathanLifschutz]

+1 to supporting POST requests. In cases where request payloads are large - such as in analytics dashboards with complex filters or sorts - POST is preferable over GET, even for read-only operations. Supporting caching in these scenarios can significantly improve performance.

[neelvirdy]

+1, @long2ice could we get help with reviewing this please?

[sleep1223]

It may also be necessary to modify the default key-builder as it does not include request.body

[ryanisn]

+1, our legacy api does not follow openapi standard, I need to keep backward compatibility