feat: adds environment variables template

Signed-off-by: Vincent Biret <vincentbiret@hotmail.com>

Author: baywet

versions/1.2.0-dev.md

@@ -182,6 +182,7 @@ This object represents one or more changes to be applied to the target document
 | Field Name | Type | Description |
 | ---- | :----: | ---- |
 | <a name="action-template-parameters"></a>parameters | [[Action template parameter object](#action-template-parameter-object)] | A list of parameters to be used during  string literal replacement. Optional. |
+| <a name="action-template-environment-variables"></a>environmentVariables | [[Action template parameter object](#action-template-parameter-object)] | A list of environment variables to be used during  string literal replacement. Optional. |
 | Any field defined in the [action object](#action-object) | mixed | The [string literal replacement syntax](#string-literal-replacement-syntax) MAY be used for any of the fields, and the replacements MUST be evaluated as the template reference is being resolved. |
 
 This object MAY be extended with [Specification Extensions](#specification-extensions).
@@ -774,13 +775,19 @@ components:
               properties:
                 '%param.propertyName%':
                   type: string
+                stageName:
+                  type: string
+                  const: '%env.stageName%'
       description: Adds an error response to the %param.pathItem% path item %param.operation% operation
       parameters:
       - name: pathItem
       - name: operation
         default: get
       - name: propertyName
         default: errorMessage
+      environmentVariables:
+      - name: stageName
+        default: dev
 actions:
 - $ref: '#/components/actionTemplates/errorResponse'
   parameterValues:
@@ -792,6 +799,8 @@ actions:
     propertyName: deleteErrorMessage
 ```
 
+> Note: in this example, not value is set for the process environment variable "stageName".
+
 ###### Result description
 
 ```yaml
@@ -813,6 +822,9 @@ paths:
                 properties:
                   errorMessage:
                     type: string
+                  stageName:
+                    type: string
+                    const: dev
   /some-items:
     delete:
       responses:
@@ -826,6 +838,9 @@ paths:
                 properties:
                   deleteErrorMessage:
                     type: string
+                  stageName:
+                    type: string
+                    const: dev
 ```
 
 ### Specification Extensions