chore: import upstream snapshot with attribution

dotnet/test/VectorData/SqlServer.ConformanceTests/README.md

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+# SQL Server Vector Store Conformance Tests
+
+This project contains conformance tests for the SQL Server Vector Store implementation.
+
+## Running the Tests
+
+By default, the tests will automatically use a testcontainer to spin up a SQL Server instance. Docker must be running on your machine for this to work.
+
+### Using an External SQL Server Instance
+
+If you want to run the tests against an external SQL Server instance (e.g., Azure SQL, a local SQL Server, or any other instance), you can provide a connection string through one of the following methods:
+
+#### Option 1: Environment Variable
+
+Set the `SqlServer__ConnectionString` environment variable:
+
+```bash
+# Bash/Linux/macOS
+export SqlServer__ConnectionString="Server=myserver.database.windows.net;Database=mydb;User Id=myuser;Password=mypassword;"
+
+# PowerShell
+$env:SqlServer__ConnectionString = "Server=myserver.database.windows.net;Database=mydb;User Id=myuser;Password=mypassword;"
+```
+
+#### Option 2: Configuration File
+
+Create a `testsettings.development.json` file in this directory with the following content:
+
+```json
+{
+  "SqlServer": {
+    "ConnectionString": "Server=myserver.database.windows.net;Database=mydb;User Id=myuser;Password=mypassword;"
+  }
+}
+```
+
+This file is git-ignored and safe for local development.
+
+#### Option 3: User Secrets
+
+```bash
+cd test/VectorData/SqlServer.ConformanceTests
+dotnet user-secrets set "SqlServer:ConnectionString" "Server=myserver.database.windows.net;Database=mydb;User Id=myuser;Password=mypassword;"
+```
+
+## Benefits of Using an External Instance
+
+Using an external SQL Server instance can be beneficial when:
+- You want to avoid the overhead of spinning up Docker containers
+- You need to test against Azure SQL specifically
+- You want faster test execution (no container startup time)
+- You're running tests in an environment where Docker is not available