Add support for the sprig functions library

[souleb]

Adresses #160

All functions are not supported, The following are discarded:

	// Date functions
	"date",
	"date_in_zone",
	"date_modify",
	"now",
	"htmlDate",
	"htmlDateInZone",
	"dateInZone",
	"dateModify",

	// Strings
	"randAlphaNum",
	"randAlpha",
	"randAscii",
	"randNumeric",
	"uuidv4",

	// OS
	"env",
	"expandenv",

	// Network
	"getHostByName",

Commit message templating can use those functions

Signed-off-by: Soule BA [email protected]

[stefanprodan]

@souleb please add a section here https://github.com/fluxcd/image-automation-controller/blob/main/docs/spec/v1beta1/imageupdateautomations.md#commit-message-template-data about spring functions and provide an example.

[squaremo]

Neatly done, thank you @souleb. I've made a couple of suggestions; see what you think, and if you're happier leaving things as they are, respond with a comment.

[squaremo]

Additionally: first PR high-five ✋ !

[souleb]

@stefanprodan anything I can do to move this forward?

[squaremo]

anything I can do to move this forward?

I think you have done all that's been asked of you 👍 You could rebase on main (removing the merge commit while you're at it), and I'll re-review, which would re-enable the merge button.

[souleb]

anything I can do to move this forward?

I think you have done all that's been asked of you 👍 You could rebase on main (removing the merge commit while you're at it), and I'll re-review, which would re-enable the merge button.

thanks @squaremo. Done!

[squaremo]

This will make lots of users happy, thank you @souleb!