[IDM-209] - feat: stripe checkout

[kiremitrov123]

Description

This pull request implements the backend logic for creating a checkout session within the Access Bridge component. It establishes the necessary interactions with the Sims and Stripe services to validate access plans and create a checkout session.

The Access Bridge now includes the following backend interactions:

Retrieve Available Plans:

• Access Bridge queries Sims for available access plans for a specified site and validates the provided access_plan_id.

Create Stripe Checkout Session:

• Upon successful plan validation, Access Bridge requests Stripe to create a checkout session. This includes sending details like price_id, mode, and redirect_url. Also, the SIMS viewer_id is added as a metadata to the checkout session.

Endpoint: POST: /v2/checkout

Jira card: Create checkout session Design document: AC-SIMS integration

According to our definition of done, I have completed the following steps:

• [x] Acceptance criteria met
• [x] Unit tests added
• [ ] Docs updated (including config and env variables)
• [ ] Translations added
• [ ] UX tested
• [ ] Browsers / platforms tested
• [ ] Rebased & ready to merge without conflicts
• [ ] Reviewed own code