feat(schema constraints): use cuelang for schema constraints

.gitlab-ci.yml

@@ -9,6 +9,7 @@
   only_branch_master_parent_repo: &only_branch_master_parent_repo
     - 'master@saltstack-formulas/template-formula'
   # `stage`
+  stage_constraints: &stage_constraints 'constraints'
   stage_lint: &stage_lint 'lint'
   stage_release: &stage_release 'release'
   stage_test: &stage_test 'test'

TEMPLATE/parameters/schema.cue

@@ -0,0 +1,46 @@
+// -*- coding: utf-8 -*-
+// vim: ft=yaml
+//
+// Constraints Schema:
+// This is not a prescriptive or forced schema! Many variants of
+// formula (and yaml data) exist in the salt user community.
+
+// template-formula
+#template: {
+    pkg?: name?: string
+    rootgroup?: string
+    hide_output?: bool
+    dir_mode?: =~"^0?[124567]{3}$" // any mode of length 3, with 0 prefix optional
+    mode?: =~"^0?[124567]{3}$" // any mode of length 3, with 0 prefix optional
+    config?:    string
+    service?: name?: string
+    subcomponent?: config: string
+
+    // legacy
+    pip_pkg?: string
+    pkgs_add?: [...]
+    pips?: [...]
+
+    // Just here for testing
+    added_in_defaults?: string
+    winner?:            string
+        ...
+}
+values?: {...#template}     // probable yaml namespace
+
+//
+// support community diversity :-)
+//
+
+template?: {...#template}   // another probable namespace
+
+Debian?: #template
+Suse?: #template
+Gentoo?: #template
+Arch?: #template
+Alpine?: #template
+FreeBSD?: #template
+OpenBSD?: #template
+Solaris?: #template
+Windows?: #template
+MacOS?: #template