[Bidder Adapter] Add AdPlayx adapter

[anuraj700]

Type of Change

• New bidder adapter
• Bug fix
• Feature / Enhancement
• Documentation update

Description

This PR adds the AdPlayx bidder adapter implementation (adplayx) to Prebid Server Java, supporting ORTB 2.6 requests for Banner and Video inventory.

Key Changes Made:

• Added AdplayxBidder.java to handle request construction with query parameters (apptoken, placementid) and bid response parsing.
• Added ExtImpAdplayx.java model for extracting adapter parameters.
• Added bidder configuration (adplayx.yaml, AdplayxConfiguration.java).
• Added parameter validation schema (static/bidder-params/adplayx.json).
• Added unit test suite AdplayxBidderTest.java targeting >80% code coverage using JUnit 5 and AssertJ.

Checklist

• Code passes checkstyle:check without line length or final modifier violations.
• Unit tests pass locally (mvn test -Dtest=AdplayxBidderTest).
• Parameters match JSON schema defined in static/bidder-params/adplayx.json.
• Added configuration in bidder-config/adplayx.yaml.

Testing Instructions

Run unit tests locally:

mvn test -Dtest=AdplayxBidderTest

### 🔧 Type of changes
- [ ] new bid adapter
- [ ] bid adapter update
- [ ] new feature
- [ ] new analytics adapter
- [ ] new module
- [ ] module update
- [ ] bugfix
- [ ] documentation
- [ ] configuration
- [ ] dependency update
- [ ] tech debt (test coverage, refactorings, etc.)

### ✨ What's the context?
What's the context for the changes?

### 🧠 Rationale behind the change
Why did you choose to make these changes? Were there any trade-offs you had to consider?

### 🔎 New Bid Adapter Checklist
- [ ] verify email contact works
- [ ] NO fully dynamic hostnames
- [ ] geographic host parameters are NOT required
- [ ] direct use of HTTP is prohibited - *implement an existing Bidder interface that will do all the job*
- [ ] if the ORTB is just forwarded to the endpoint, use the generic adapter - *define the new adapter as the alias of the generic adapter*
- [ ] cover an adapter configuration with an integration test

### 🧪 Test plan
How do you know the changes are safe to ship to production?

### 🏎 Quality check
- [ ] Are your changes following [our code style guidelines](https://github.com/prebid/prebid-server-java/blob/master/docs/developers/code-style.md)?
- [ ] Are there any breaking changes in your code?
- [ ] Does your test coverage exceed 90%?
- [ ] Are there any erroneous console logs, debuggers or leftover code in your changes?