feat: add jwt pkg (#14928)

- Adds a `jwtutils` package to be shared amongst the various
packages in the codebase that make use of JWTs. It's intended to help us
standardize on one library instead of some implementations using
`go-jose` and others using `golang-jwt`.

The main reason we're converging on `go-jose` is due to its support for
JWEs, `golang-jwt` also has a repo to handle it but it doesn't look
maintained: https://github.com/golang-jwt/jwe

go.mod

@@ -207,6 +207,7 @@ require (
 	github.com/coder/serpent v0.8.0
 	github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21
 	github.com/emersion/go-smtp v0.21.2
+	github.com/go-jose/go-jose/v4 v4.0.2
 	github.com/gomarkdown/markdown v0.0.0-20231222211730-1d6d20845b47
 	github.com/google/go-github/v61 v61.0.0
 	github.com/mocktools/go-smtp-mock/v2 v2.3.0
@@ -224,7 +225,6 @@ require (
 	github.com/charmbracelet/x/ansi v0.2.3 // indirect
 	github.com/charmbracelet/x/term v0.2.0 // indirect
 	github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f // indirect
-	github.com/go-jose/go-jose/v4 v4.0.2 // indirect
 	github.com/go-viper/mapstructure/v2 v2.0.0 // indirect
 	github.com/hashicorp/go-plugin v1.6.1 // indirect
 	github.com/hashicorp/go-retryablehttp v0.7.7 // indirect