Add Sprig to the golang templating

[spirilis]

Can we add Sprig to the golang templating for the templates? I'm addicted to Sprig's suite of functions from using Helm, and I'm missing it a bit right now.

Sprig is easy to use:

https://pkg.go.dev/github.com/Masterminds/sprig/v3

Example from one of my test harnesses:

Import-

import (
	"os"
	"testing"
	"text/template"

	sprig "github.com/Masterminds/sprig/v3"
)

Including it in the template chain:

tp := template.Must(template.New("test").Funcs(sprig.FuncMap()).Parse(testTemp))

Example template:

var testTemp = `
{
	[
		{{range .Items -}}
		{{ . | upper }}
		{{end}}
	]
}
`

Output:

go test -run BasicTemplate

{
        [
                STR1
                STR2
                STR3
                STR4

        ]
}
PASS

[luka5]

Even if it was already argued against introducing it in 2018 in #1651, I would also like to use it in Alertmanager. It's especially useful for those who are currently migrating from prometheus-msteams to the new built-in Alertmanager MS Teams (thanks for that!).

[grobinson-grafana]

There is a discussion on this here.