chore(validation): move functions from constants

- Move validation functions from `internal/constants` to `internal/configuration/settings/validation`
- Concatenate all OpenVPN constants in `internal/constants/openvpn.go`

internal/provider/vyprvpn/openvpnconf.go

@@ -65,7 +65,7 @@ func (v *Vyprvpn) BuildConf(connection models.Connection,
 	}
 
 	lines = append(lines, utils.WrapOpenvpnCA(
-		constants.VyprvpnCertificate)...)
+		constants.VyprvpnCA)...)
 
 	lines = append(lines, "")