Preserve text indentation

Match tabs and spaces leading the token so that indentation is preserved
when inserting hints.

ee/app/assets/javascripts/security_configuration/api_fuzzing/utils.js

@@ -11,7 +11,15 @@ export const insertTip = ({ snippet, tip, token }) => {
   if (!isString(token)) {
     throw new Error('token must be a string');
   }
-  return snippet.replace(token, `# ${tip}\n${token}`);
+  const lines = snippet.split('\n');
+  for (let i = 0; i < lines.length; i += 1) {
+    if (lines[i].includes(token)) {
+      const indent = lines[i].match(/^[ \t]+/)?.[0] ?? '';
+      lines[i] = lines[i].replace(token, `# ${tip}\n${indent}${token}`);
+      break;
+    }
+  }
+  return lines.join('\n');
 };
 
 export const insertTips = (snippet, tips = []) =>

ee/spec/frontend/security_configuration/api_fuzzing/utils_spec.js

@@ -43,6 +43,27 @@ describe('insertTip', () => {
       }),
     ).toBe(expected);
   });
+
+  it('preserves indentation', () => {
+    const snippet = `---
+default:
+  artifacts:
+    expire_in: 30 days`;
+
+    const expected = `---
+default:
+  artifacts:
+    # a very helpful tip
+    expire_in: 30 days`;
+
+    expect(
+      insertTip({
+        snippet,
+        token: 'expire_in:',
+        tip,
+      }),
+    ).toBe(expected);
+  });
 });
 
 describe('insertTips', () => {