fix: include incoming message size when checking against batch size

[kwvg]

Expected behavior

• Create StatsdClient with batchsize
• Push a few messages that are under batchsize, remains in same batch
• Push a message that would go over batchsize if appended, gets put into a new batch
• Trigger flush, two batches are created, both under batchsize

Actual behavior

• Create StatsdClient with batchsize
• Push a few messages that are under batchsize, remains in same batch
• Push a message that would go over batchsize if appended, gets put into same batch
• Flush triggered, one batch is created exceeding batchsize

Steps to reproduce

• Revert e3bffa3 and run tests, a hyphen (-) is used to indicate a batch

[kevinkreiser]

@kwvg the documentation https://github.com/vthiery/cpp-statsd-client?tab=readme-ov-file#batching explicitly states that the batch size is not a hard limit (indeed it cant be without quite a bit of annoyance, eg. in the case where the batch size is so small a single message wouldnt fit). so i wouldnt characterize this change as a "fix" in this case. this is merely just more of an attempt to make batch size a hard limit right? but even still, the change here does not make it a hard limit specifically in the example i mentioned above. i also see that you keep the additional memory reservation when adding a new batch, which makes no sense if we are trying to stick to a hard limit.

at any rate, i think we should first discuss the merits of a hard limit vs the practical reality. perhaps we can throw or something if someone wants to make a batch size that is too small to be reasonable so as to avoid the pitfall i mentioned above? at present i dont feel strong about having a hard limit vs a soft limit. the reason why we went with a soft one though in the first place was simply because it was just quite a bit less difficult to adhere to logically 😄

[kevinkreiser]

if we really do want a hard limit we should add some fuzz to the batch size for overages:

Suggested change

	m_batchingMessageQueue.back().reserve(m_batchsize + 256);
	m_batchingMessageQueue.back().reserve(m_batchsize);

[kevinkreiser]

linting step is broken we'll have to fix that on our end. you can ignore that for now 😄