Added README.md

Author: ItielOlenick

tests/test-e2e-apps/metrics-basic-auth/README.md

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+# Metrics Basic Auth E2E Test App
+Simple web application used in an end-to-end (E2E) test to verify that the OpenTelemetry collector can retrieve secret authentication details from the target allocator over mTLS.
+
+## Overview
+The web app provides a metrics endpoint secured with basic authentication, simulating real-world scenarios where services require secure access to their metrics. 
+
+## Usage
+This app is used within the E2E test suite to verify the OpenTelemetry operator's handling of mTLS-secured communications.