Restored original EnsureTrailingSlash

[tracyboehrer]

Fixes #278

Dueling merges caused a bit of confusion.

[Copilot]

Pull Request Overview

This PR restores the original behavior of the EnsureTrailingSlash method to address issue #278.

• Changes the access modifier from public to internal, aligning with the intended API design.
• Updates the trailing slash condition check by replacing Contains with EndsWith for accuracy.

Comments suppressed due to low confidence (2)

src/libraries/Client/Microsoft.Agents.Connector/RestClients/UriExtensions.cs:34

• Changing the access modifier from public to internal will restrict external access; verify that this change is intended based on the original API design.

internal static Uri EnsureTrailingSlash(this Uri uri)

src/libraries/Client/Microsoft.Agents.Connector/RestClients/UriExtensions.cs:40

• Replacing the condition from Contains to EndsWith correctly targets the trailing slash; ensure that all potential URI formats are properly handled.

if (!uriString.EndsWith('/'))