[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:

• Acceptance criteria met
• 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

[github-actions]

Visit the preview URL for this PR (updated for commit 3c4220f):

https://ottwebapp--pr587-idm-209-stripe-check-vl8fsm9t.web.app

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