Validate links in CLI forms

[TheJolman]

Many of the CLI forms require links to be input, but there's nothing to check if these are actually valid URLs.

[GaballaGit]

Useful information: Go’s standard library offers a url package, this url package has a Parse function you can use.

[TheJolman]

@Samsondu not sure if you've worked on this at all or not, but the CLI is in the midst of a big refactor so I would avoid touching anything outside of internal/cli/announcements as they are going to be changed somewhat soon. However, the announcements package should be somewhat stable now and does need some validators written for it. The announcement form looks like:

And most of these fields need a validator written for them. Check out the huh readme, but these validators can be written inline like:

        huh.NewInput().
            Title("What’s your name?").
            Value(&name).
            // Validating fields is easy. The form will mark erroneous fields
            // and display error messages accordingly.
            Validate(func(str string) error {
                if str == "Frank" {
                    return errors.New("Sorry, we don’t serve customers named Frank.")
                }
                return nil
            }),

OR if you can write reusable functions like the existing ValidateNonEmpty() function in the internal/cli/forms like:

// Used for fields that must contain a value
func ValidateNonEmpty() func(string) error {
	return func(field string) error {
		if field == "" {
			return errors.New("field must contain a value")
		}
		return nil
	}
}

and then used like

			huh.NewInput().
				Title("Announcement Visibility").
				Value(&payload.Visibility).
				Validate(forms.ValidateNonEmpty()),

Pls lmk if you need any help at all getting started or anything at all :)