# This PR
Supports the env var `DD_API_KEY_SECRET_RELOAD_INTERVAL`, in seconds. It
applies when Datadog API Key is set using `DD_API_KEY_SECRET_ARN`. For
example:
- if it's `120`, then api key will be reloaded about every 120 seconds.
Note that reload can only be triggered when api key is used, usually
when data is being flushed. If there is no invocation and no data needs
to be flushed, then reload won't happen.
- If it's not set or set to `0`, then api key will only be loaded once
the first time it is used, and won't be reloaded.

# Motivation
Some customers regularly rotate their api key in a secret. We need to
provide a way for them to update our cached key.
#834

# Testing
## Steps
1. Set the env var `DD_API_KEY_SECRET_RELOAD_INTERVAL` to `120`

2. Invoke the Lambda every minute

## Result
The reload interval is passed to the `ApiKeyFactory`
<img width="711" height="25" alt="image"
src="https://github.com/user-attachments/assets/6fcc5081-accb-4928-8fa7-094d36aa2fa1"
/>

Reload happens roughly every 120 seconds. It's sometimes longer than 120
seconds due to the reason explained above.
<img width="554" height="252" alt="image"
src="https://github.com/user-attachments/assets/3fa78249-ff98-47d2-a953-f090630bbeb1"
/>

# Notes to Users
When you use this env var, please also keep a grace period for the old
api key after you update the secret to the new key, and make the grace
period longer than the reload interval to give the extension sufficient
time to reload the secret.

# Internal Notes
Jira: https://datadoghq.atlassian.net/browse/SVLS-7572