Add MCP Listener and Service APIs for Ballerina proposal

[AzeemMuzammil]

Purpose

fixes: ballerina-platform/ballerina-library#7996

Goals

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Approach

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User stories

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Release note

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Documentation

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Training

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Certification

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Marketing

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Automation tests

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Security checks

• Followed secure coding standards in http://wso2.com/technical-reports/wso2-secure-engineering-guidelines? yes/no
• Ran FindSecurityBugs plugin and verified report? yes/no
• Confirmed that this PR doesn't commit any keys, passwords, tokens, usernames, or other secrets? yes/no

Samples

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Learning

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[Copilot]

Pull Request Overview

This PR introduces a proposal document for the MCP Listener and Service APIs for Ballerina, outlining a comprehensive design for building MCP servers with support for streamable HTTP transport and both basic and advanced service patterns.

• Adds a detailed proposal document with architecture, design strategy, and example usage for MCP servers.
• Outlines the differences between basic services (with automatic tool discovery) and advanced services (with manual tool management).

[CLAassistant]

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