feat: add additional fields to EnterpriseLearnerOfferApiSerializer

[adamstankiewicz]

Description

Adds the following fields to EnterpriseLearnerOfferApiSerializer in support of ENT-6960:

• enterprise_customer_uuid
• max_user_applications
• remaining_applications
• remaining_applications_for_user

Also adds the remaining_applications to EnterpriseAdminOfferApiSerializer.

Related PRs:

• feat: add Card.Status to course run cards for error state UX messaging openedx/frontend-app-learner-portal-enterprise#732

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Required Testing

• Before deploying this change, complete a purchase in the stage environment.
  (^ We can remove that manual check once REV-2624 is done and the corresponding e2e test runs again)

Description

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• Which edX user roles will this change impact? Common user roles are "Learner", "Course Author", "Developer", and "Operator".
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[iloveagent57]

question unrelated to your change: why are we returning a string-ified number in this serializer?

[adamstankiewicz]

I think the answer to this might be covered in the response to your other comment?

[iloveagent57]

why is balance str()-ed but applications are (presumably) ints?

[adamstankiewicz]

@iloveagent57 I think the current state of the enterprise-learner-offers endpoint returns the balance as a str() because course-discovery also returns price as a string, presumably so that clients don't have to format the returned value to have the 2 decimals. If returning a float with the UI wanted to display the price as $199.00, would need to transform 199 or 199.0 to 199.00 for display purposes, where if its given by the API as a string, the client can just render it as is.

For this purpose of this PR, I'm just following convention with what already exists. That said, I'm not sure what the "standard"/"correct" way of returning price should be. I could see some tradeoffs with both approaches.

I kept applications as ints because there's no chance for them to be floats; the decimal formatting is a non-issue for applications.