template: Support base64-encoding data file contents

This is done with a new `base64` parameter property:

```yaml
definitions:
    var:
        dataFile: example
        base64: true
    template: |
        {{var}}
```

Author: mstokes-f5

README.md

@@ -320,6 +320,16 @@ Parameters with a `dataFile` property:
 * have their `default` set to the contents of the file
 * given a default `format` of `hidden`
 
+Additionally, the contents of the data file can be base64 encoded before being used as for `default` by setting the `base64` property to `true`:
+
+```yaml
+definitions:
+    var:
+        dataFile: example
+        base64: true
+    template: |
+        {{var}}
+```
 
 ## Development
 

lib/template.js

@@ -410,7 +410,13 @@ class Template {
                     if (!propDef.format) {
                         propDef.format = 'hidden';
                     }
-                    propDef.default = dataFiles[propDef.dataFile];
+
+                    const dataFile = dataFiles[propDef.dataFile];
+                    if (propDef.base64) {
+                        propDef.default = Buffer.from(dataFile, 'utf8').toString('base64');
+                    } else {
+                        propDef.default = dataFile;
+                    }
                     delete propDef.dataFile;
                 }
                 break;

test/template.js

@@ -1257,10 +1257,14 @@ describe('Template class tests', function () {
             definitions:
                 fromFile:
                     dataFile: textData.txt
+                base64:
+                    dataFile: textData.txt
+                    base64: true
             template: |-
                 {{fromFile}}
+                {{base64}}
         `;
-        const reference = 'Lorem ipsum\n';
+        const reference = 'Lorem ipsum\n\nTG9yZW0gaXBzdW0K';
         return Template.loadYaml(yamldata, { dataProvider })
             .then((tmpl) => {
                 const schema = tmpl.getParametersSchema();
@@ -1272,6 +1276,8 @@ describe('Template class tests', function () {
                 assert.strictEqual(fileProp.format, 'hidden');
                 assert.strictEqual(fileProp.default, 'Lorem ipsum\n');
 
+                assert.strictEqual(schema.properties.base64.default, 'TG9yZW0gaXBzdW0K');
+
                 const rendered = tmpl.render();
                 console.log(rendered);
                 assert.strictEqual(rendered, reference);