feat: translate STUDIO_BASE_URL to cmsBaseUrl in frontend site config

[arbrandes]

Description

Maps the legacy STUDIO_BASE_URL key to the optional cmsBaseUrl field in SITE_CONFIG_TRANSLATION_MAP, matching frontend-base's OptionalSiteConfig interface. With this change, FrontendSiteConfigView surfaces the Studio base URL at the top level of the response rather than nesting it inside commonAppConfig.

The two test_views.py cases that previously asserted STUDIO_BASE_URL lived in commonAppConfig now assert it appears at the top level as cmsBaseUrl.

LLM usage notice

Built with assistance from Claude.

[brian-smith-tcril]

Logic looks good. Couple little comments about test readability but I don't think those should block merging this.

[brian-smith-tcril]

This block is a little confusing. I understand the change in this PR is verifying that we don't have STUDIO_BASE_URL in commonAppConfig because it's instead in siteConfig, but putting it in the

# Unmapped MFE_CONFIG keys appear in commonAppConfig (not at the top level)

section doesn't provide that context.

I think splitting this block up a little into

Suggested change

	# Site-level key translated to top level
	# Site-level keys translated to top level
	self.assertEqual(data["lmsBaseUrl"], "https://courses.example.com") # noqa: PT009
	self.assertEqual(data["cmsBaseUrl"], "https://studio.example.com") # noqa: PT009
	# Unmapped MFE_CONFIG keys appear in commonAppConfig (not at the top level)
	self.assertNotIn("CREDENTIALS_BASE_URL", data) # noqa: PT009
	common = data["commonAppConfig"]
	self.assertEqual(common["CREDENTIALS_BASE_URL"], "https://credentials.example.com") # noqa: PT009
	self.assertEqual(common["STUDIO_BASE_URL"], "https://studio.example.com") # noqa: PT009
	self.assertNotIn("STUDIO_BASE_URL", common) # noqa: PT009
	common = data["commonAppConfig"]
	# Site-level keys are translated to top level
	self.assertEqual(data["lmsBaseUrl"], "https://courses.example.com") # noqa: PT009
	self.assertEqual(data["cmsBaseUrl"], "https://studio.example.com") # noqa: PT009
	# Site-level keys translated to top level don't appear in commonAppConfig
	self.assertNotIn("LMS_BASE_URL", common) # noqa: PT009
	self.assertNotIn("STUDIO_BASE_URL", common) # noqa: PT009
	# Unmapped MFE_CONFIG keys appear in commonAppConfig (not at the top level)
	self.assertNotIn("CREDENTIALS_BASE_URL", data) # noqa: PT009
	self.assertEqual(common["CREDENTIALS_BASE_URL"], "https://credentials.example.com") # noqa: PT009

[brian-smith-tcril]

Similar comment to my previous one, feels odd to be using assertNotIn on common in the "Unmapped keys are preserved in commonAppConfig" block