docs: Document duplicate license message behavior and fixes

[Copilot]

When AutoMapper is registered or configured multiple times, users see duplicate license log messages at startup. This adds a dedicated section to License-configuration.md covering the cause and remedies.

Changes

• docs/source/License-configuration.md — New Multiple License Messages section with:
  • AddAutoMapper (MS.Ext.DI): Clarifies that multiple calls are safe — IMapper is only registered once, so license validation runs exactly once regardless of how many AddAutoMapper calls appear in startup code.
  • MapperConfiguration directly: Each instance runs its own license validation. Fix is to create one instance and reuse it as a singleton.
  • Suppression: For cases where multiple configurations are intentional (e.g. test suites), filter the log category:

builder.Logging.AddFilter("LuckyPennySoftware.AutoMapper.License", LogLevel.None);

Original prompt

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This section details on the original issue you should resolve

<issue_title>Document fixes to multiple license messages</issue_title>
<issue_description>From #4609

With AutoMapper enforcing licensing at startup, if users register or configure AutoMapper multiple times, they often see duplicate license messages.

Document this behavior and corrections explicitly in the docs.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Document fixes to multiple license messages #4611

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