feat: add TTL configuration for function response

[alperencelik]

Description of your changes

This PR aims to make the TTL value of the function configurable via DeploymentRuntimeConfig.

Fixes #170

I have:

• Read and followed Crossplane's contribution process.
• Added or updated unit tests for my change.

[alperencelik]

Also if you guys agree, once this merged I think we can backport it to the function-template-go

[Ata-NovacekJan]

Hi @alperencelik , may I ask what drove this change on your side?
We're facing performance issues after switching to realtime compositions and came to conclusion that the response's TTL is the root cause, so wondering if we are the only ones with such as problem. We ended up with fork + own implementation (as function arguments - so you can set the TTL in function call in composition pipeline).
It's quite a downer tbh as we were really looking forward to get better performance out of Crossplane v2, we basically got poll-based reconciliation with hardcoded 1 minute interval.

[alperencelik]

Hi @alperencelik , may I ask what drove this change on your side? We're facing performance issues after switching to realtime compositions and came to conclusion that the response's TTL is the root cause, so wondering if we are the only ones with such as problem. We ended up with fork + own implementation (as function arguments - so you can set the TTL in function call in composition pipeline). It's quite a downer tbh as we were really looking forward to get better performance out of Crossplane v2, we basically got poll-based reconciliation with hardcoded 1 minute interval.

Hi @Ata-NovacekJan, I was observing that my function has been invoked quite frequently and am trying to understand the underlying reason behind it. The problem is that my current function is unfortunately too heavy to operate (even runFunction took ~30 s). I modified the TTL on my function response to the amount that I need, but since I do have a function pipeline in my composition, the last step of the pipeline (function-auto-ready) is always sending the TTL as 1 minute. It's causing my function to run unnecessarily and do the heavy work over and over again. I'm currently in a state where I don't have that many actors that can interfere with my resources, so I just would like to set the TTL for a reasonable time to reconcile after.