[FEATURE] [MER-3295] Course enrollment error

[Francisco-Castro]

Ticket: MER-3295

This PR modifies the text message shown when an enrollment course link is invalid or expired. It also moves the invalid enrollment link endpoint to avoid an unnecessary account check-in. Additionally, it includes a refactor of the RequireSection module to improve readability.

https://github.com/Simon-Initiative/oli-torus/assets/47334502/fbb0a031-c7c3-4dc1-bcf3-88913f65bc94

[darrensiegel]

We should never be embedding "OLI" or "Torus" anywhere in user facing UI. Instead, use the appropriate value from the collection of "Vendor Properties". Look in config.exs to see this collection and their default values:

config :oli, :vendor_property,
  workspace_logo:
    System.get_env("VENDOR_PROPERTY_WORKSPACE_LOGO", "/branding/prod/oli_torus_icon.png"),
  product_full_name:
    System.get_env("VENDOR_PROPERTY_PRODUCT_FULL_NAME", "Open Learning Initiative"),
  product_short_name: System.get_env("VENDOR_PROPERTY_PRODUCT_SHORT_NAME", "OLI Torus"),
  product_description:
    System.get_env(
      "VENDOR_PROPERTY_PRODUCT_DESCRIPTION",
      default_description
    ),
  product_learn_more_link:
    System.get_env("VENDOR_PROPERTY_PRODUCT_LEARN_MORE_LINK", "https://oli.cmu.edu"),
  company_name: System.get_env("VENDOR_PROPERTY_COMPANY_NAME", "Carnegie Mellon University"),
  company_address:
    System.get_env(
      "VENDOR_PROPERTY_COMPANY_ADDRESS",
      "5000 Forbes Ave, Pittsburgh, PA 15213 US"
    ),
  support_email: System.get_env("VENDOR_PROPERTY_SUPPORT_EMAIL")

[Francisco-Castro]

@darrensiegel I have applied the requested changes. Please let me know if you have any other suggestions.