api: add hardcoded versioning support

Added the _VERSION variable to the exported table.
Is part of the task [1].

1. github.com/tarantool/roadmap-internal/issues/204

Author: GRISHNOV

.github/workflows/publish.yml

@@ -6,8 +6,18 @@ on:
     tags: ['*']
 
 jobs:
+  # Run not only on tags, otherwise dependent job will skip.
+  version-check:
+    runs-on: ubuntu-20.04
+    steps:
+      - name: Check module version
+        uses: tarantool/actions/check-module-version@igrishnov/gh-204-add-hardcoded-versioning-support
+        with:
+          module-name: 'graphql'
+
   publish-rockspec-scm-1:
     if: github.ref == 'refs/heads/master'
+    needs: version-check
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
@@ -18,6 +28,7 @@ jobs:
 
   publish-rockspec-tag:
     if: startsWith(github.ref, 'refs/tags/')
+    needs: version-check
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2

graphql-scm-1.rockspec

@@ -21,6 +21,7 @@ build = {
   type = 'builtin',
   modules = {
     ['graphql.init'] = 'graphql/init.lua',
+    ['graphql.version'] = 'graphql/version.lua',
     ['graphql.execute'] = 'graphql/execute.lua',
     ['graphql.introspection'] = 'graphql/introspection.lua',
     ['graphql.parse'] = 'graphql/parse.lua',

graphql/init.lua

@@ -1 +1 @@
-return {VERSION = 'unknown'}
+return {_VERSION = require('graphql.version')}

graphql/version.lua

@@ -0,0 +1,4 @@
+-- Сontains the module version.
+-- Requires manual update in case of release commit.
+
+return '0.2.0'

test/unit/graphql_test.lua

@@ -1090,7 +1090,7 @@ function g.test_util_find_by_name()
 end
 
 g.test_version = function()
-    t.assert_type(require('graphql').VERSION, 'string')
+    t.assert_type(require('graphql')._VERSION, 'string')
 end
 
 function g.test_is_array()