DKIM Signing Module `cache_key` and `cache_expiry` options

[rob4226]

Hi,

A DKIM signing guide document page references options named cache_key and cache_expiry listed in the performance section. I don't see any reference to these options anywhere else in the docs nor in the source code for the DKIM signing module. Is this section correct?

docs.rspamd.com/docs/tutorials/dkim_signing_guide.md

Lines 1240 to 1249 in 8ebf18f

	### Performance Optimization
	1. **Key caching**:
	```hcl
	# /etc/rspamd/local.d/dkim_signing.conf
	# Cache keys in memory
	cache_key = true;
	cache_expiry = 3600;
	```

Also, the next section lists an option sign_inbound:

docs.rspamd.com/docs/tutorials/dkim_signing_guide.md

Line 1256 in 8ebf18f

sign_inbound = false; # Never sign inbound

I see the ARC module has this option but does the DKIM signing module also have this option? I didn't see it listed in other DKIM signing module document pages or the default config file.

Thanks.