docs: adding affilaitions api (CM-1042)

[ulemons]

Note

Low Risk
Documentation-only change adding an OpenAPI contract for existing endpoints; no runtime behavior or data handling logic is modified.

Overview
Adds a new openapi.yaml describing the public v1 Affiliations API, including POST /affiliations (bulk lookup with pagination) and GET /affiliations/{githubHandle} (single lookup).

The spec defines bearer API-key security, response/error schemas (Contributor, AffiliationPeriod, BulkAffiliationsResponse, HttpError), and standard error responses (400/401/403/404/429).

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✅ joanagmaia
❌ ulemons
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[Copilot]

Pull request overview

Adds an OpenAPI specification for the Public v1 “Affiliations” endpoints to document bulk and single-handle contributor affiliation lookups.

Changes:

• Introduces a new openapi.yaml describing POST /affiliations (bulk lookup with pagination) and GET /affiliations/{githubHandle} (single lookup).
• Defines request/response schemas and common error responses (400/401/403/404/429) for the Affiliations API.

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