feat(helm): Add support for initContainers.

[pantierra]

This could be useful when the auth server is deployed with stac-auth-proxy and we need to wait.
At least in eoAPI would be good for testing (developmentseed/eoapi-k8s#358).

[alukach]

I'll be honest that this is a bit beyond my knowledge but it appears reasonable

[alukach]

I should also note that today, the STAC Auth Proxy does do a wait for the upstream STAC API to be available before accepting requests:

stac-auth-proxy/src/stac_auth_proxy/lifespan.py

Lines 31 to 63 in 5ce9487

	async def check_server_health(
	url: str | HttpUrl,
	max_retries: int = 10,
	retry_delay: float = 1.0,
	retry_delay_max: float = 5.0,
	timeout: float = 5.0,
	) -> None:
	"""Wait for upstream API to become available."""
	# Convert url to string if it's a HttpUrl
	if isinstance(url, HttpUrl):
	url = str(url)
	async with httpx.AsyncClient(
	base_url=url, timeout=timeout, follow_redirects=True
	) as client:
	for attempt in range(max_retries):
	try:
	response = await client.get("/")
	response.raise_for_status()
	logger.info(f"Upstream API {url!r} is healthy")
	return
	except httpx.ConnectError as e:
	logger.warning(f"Upstream health check for {url!r} failed: {e}")
	retry_in = min(retry_delay * (2**attempt), retry_delay_max)
	logger.warning(
	f"Upstream API {url!r} not healthy, retrying in {retry_in:.1f}s "
	f"(attempt {attempt + 1}/{max_retries})"
	)
	await asyncio.sleep(retry_in)
	raise RuntimeError(
	f"Upstream API {url!r} failed to respond after {max_retries} attempts"
	)

[pantierra]

At least in Kubernetes, initContainers would allow to configure the waiting for the Stac API being up and running.

[batpad]

Seems like this just adds support to allow someone deploying this to add a custom init container? Seems good to me, if being able to configure that is useful, makes sense 👍

[batpad]

Hmm am seeing CI failures that seem unrelated to this commit. Not sure what's going on there.

[pantierra]

Thanks for your reviews! Yes, the errors seemed unrelated to me, too. Can this be merged?

[alukach]

@pantierra good to go now