feat: add validation to issue badge

[luisfelipec95]

Description

This change adds an optional, settings-driven badge issuance restriction check for Credly badges.

When enabled, the badge completion flow evaluates whether badge issuance is allowed by querying a configurable external API for each related course fulfillment before issuing the badge. If any exact course match indicates that badge issuance is restricted, the badge is not issued.

The restriction logic is kept separate from the signal handler, and authenticated requests use the existing SiteConfiguration.api_client and OAuthAPIClient implementation.

This feature is disabled by default and is designed to remain generic so it can support different integrations.

Changes

Added a new feature flag:

• BADGES_ENABLE_ISSUANCE_RESTRICTIONS

Added configurable settings for the external restrictions check:

• BADGES_ISSUANCE_RESTRICTIONS_API_URL
• BADGES_ISSUANCE_RESTRICTIONS_FLAG_NAME

Added a course_key field to badge fulfillments:

• stores the course identifier associated with the fulfillment
• allows badge issuance checks to be evaluated in a course-specific context

Added a dedicated badge restriction utility:

• keeps the external restriction check separate from handle_badge_completion
• evaluates all relevant fulfillment course keys
• matches the exact ccx_id returned by the external API
• blocks issuance when the configured restriction flag is false
• allows issuance by default when the feature is disabled or no restriction data is available

Updated handle_badge_completion to:

• run the restriction check only for Credly badges
• retrieve the user's badge progress and related fulfillments
• query the external API using each fulfillment's course_key
• use the existing SiteConfiguration.api_client for authenticated inter-service requests
• skip badge issuance when the external API indicates that issuance is not allowed

Why

Some deployments need badge issuance to depend on external business rules. This change introduces a flexible mechanism to evaluate those rules at issuance time while keeping the default behavior unchanged for the community.

The course_key field is required so each fulfillment carries the course identifier needed to evaluate issuance restrictions on a per-course basis.

Reusing SiteConfiguration.api_client avoids duplicating OAuth2 client-credentials logic that is already provided by Credentials and edx-rest-api-client, including token handling and refresh behavior.

Default behavior

This feature is disabled by default.

When BADGES_ENABLE_ISSUANCE_RESTRICTIONS is disabled, or when no matching restriction data is returned by the external API, badge issuance continues as before.

[openedx-webhooks]

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[GlugovGrGlib]

@luisfelipec95 Thanks for the PR. Before I proceed with review can you please create a new Issue in the repository describing this as functionality request with business need details and acceptance criteria or definition of done.

Additionally, can you please include documentation updates into this PR because in other case this new feature is basically invisible for Open edX users.

[luisfelipec95]

Hi @GlugovGrGlib, I create this issue #3011 and updated the PR, thanks.