feat(marketing): add ability to override brand

[stephenliang]

This PR adds a header which allows UI tests to override the brand to allow the same "All the Things" code that is in the Code.org space to be used for CSForAll to eliminate the need to maintain multiple experiences and sync them together.

[Copilot]

Pull Request Overview

This PR adds the ability to override the brand selection through an HTTP header (x-brand-override) for UI testing purposes. This allows the same codebase to be used across different brand experiences (Code.org, CSForAll) without maintaining separate implementations.

• Added support for brand override via HTTP header in middleware
• Created new utility function to parse brand strings
• Updated brand resolution logic to prioritize header override over hostname-based detection

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
frontend/apps/marketing/src/middleware/withBrand.ts	Modified middleware to check for x-brand-override header and use it for brand selection
frontend/apps/marketing/src/config/brand.ts	Added getBrandFromString function to parse brand values from string input

[Copilot]

The function should validate that the input string matches expected Brand enum values rather than using a switch statement with hardcoded strings. Consider using Object.values(Brand).includes(brandString as Brand) for more robust validation.

Suggested change

	switch (brandString) {
	case Brand.CODE_DOT_ORG:
	return Brand.CODE_DOT_ORG;
	case Brand.HOUR_OF_CODE:
	return Brand.HOUR_OF_CODE;
	case Brand.CS_FOR_ALL:
	return Brand.CS_FOR_ALL;
	default:
	return undefined;
	}
	if (brandString && Object.values(Brand).includes(brandString as Brand)) {
	return brandString as Brand;
	}
	return undefined;

[stephenliang]

The switch/case is more legible and provides the same behavior.