Remove base64 encoding from files that contain plain text

What does this MR do?

This merge request fixes the issue where files containing plain text were base64 encoded after being uploaded from the WebIDE.

Any file without the text/* mime type is base64 encoded and as a result, the contents of the file in the repo was base64 encoded even if it contains plain text.

This MR prevents this issue by removing the base64 encoding if the file contains plain text.

What are the relevant issue numbers?

Closes: #48746 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines

screen_rec

spec/javascripts/ide/components/new_dropdown/upload_spec.js

@@ -57,14 +57,13 @@ describe('new dropdown upload', () => {
   describe('createFile', () => {
     const textTarget = {
       result: 'base64,cGxhaW4gdGV4dA==',
-      type: 'text/plain',
     };
     const binaryTarget = {
       result: 'base64,w4I=',
-      type: 'image/png',
     };
     const file = {
       name: 'file',
+      type: 'text/plain',
     };
 
     it('creates file in plain text (without encoding) if the file content is plain text', () => {
@@ -78,6 +77,8 @@ describe('new dropdown upload', () => {
       });
     });
 
+    file.type = 'image/png';
+
     it('splits content on base64 if binary', () => {
       vm.createFile(binaryTarget, file);