New endpoint: GET /v1/analytics/conversions/

[freddyDOTCMS]

Description

Create a new endpoint GET /v1/analytics/conversions that returns one row per conversion definition with its totals and top 3 attributed content items.

Improvement plan: https://docs.google.com/document/d/1hVfIurPqAJJ1PN1EalmvrWXnGNt5sY21MI-409lrXpU/edit?tab=t.klqavlz4cis7#heading=h.8vek9yxwq8yt

Parent epic: #35048

Query Parameters

Param	Required	Description
siteId	✅	dotCMS site identifier
environment	✅	Cluster/environment identifier
from + to OR range	✅	Time range — absolute or relative
conversionName	❌	Filter by conversion name
orderBy	❌	conversionName, totalConversions, convRate
orderDir	❌	asc or desc
page	❌	Page number
pageSize	❌	Results per page

Headers

X-Customer-Id, X-Signature (HMAC-SHA256)

Time range rules

• If from/to present → use them, ignore range
• Else if range present → compute from/to

Response shape

{
  "params": { "siteId": "...", "environment": "...", "from": "...", "to": "..." },
  "pagination": { "page": 1, "pageSize": 50, "totalPages": 2, "totalItems": 60 },
  "data": [
    {
      "conversionName": "download",
      "totalConversions": 320,
      "convRate": 42.15,
      "topAttributedContent": [
        {
          "identifier": "/landing/product",
          "title": "Product Landing Page",
          "eventType": "page_view",
          "attributionCount": 180,
          "events": 890,
          "attributionRate": 20.22
        }
      ]
    }
  ]
}

Acceptance Criteria

• GET /v1/analytics/conversions/summary endpoint created
• Mandatory params validated: siteId, environment, time range — returns 400 when missing
• conversionName optional filter works correctly
• orderBy supports all three values; orderDir defaults to desc
• Pagination works: correct totalPages / totalItems in response
• Each row includes up to top 3 attributed content items with full attribution fields
• Time range rules applied: absolute takes precedence over relative
• X-Customer-Id enforces row-level data isolation
• X-Signature validated (HMAC-SHA256)
• Response matches the documented JSON shape

Additional Context

• Source task: Conversion dashboard endpoints / Conversion Endpoint Detail changes
• Requires Phase 2 completion — blocked by: Update ClickHouse Materialized Views after lookup table removal #35062
• Related: New endpoint: GET /v1/analytics/content/attribution #35076 (content/attribution endpoint feeds the topAttributedContent logic)
• Related branch: issue-34849-Add-dotCMS-Analytics-Proxy-Endpoint-for-/v1/analytics/-to-dot-ca-event-manager