Bump MediatR from 8.0.2 to 12.4.0 in /src

Bumps [MediatR](https://github.com/jbogard/MediatR) from 8.0.2 to 12.4.0.
- [Release notes](https://github.com/jbogard/MediatR/releases)
- [Commits](LuckyPennySoftware/MediatR@v8.0.2...v12.4.0)

---
updated-dependencies:
- dependency-name: MediatR
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

Directory.Build.props

@@ -44,7 +44,7 @@
         <WalletFrameworkIndySdkVersion>2.0.1</WalletFrameworkIndySdkVersion>
         <HyperledgerIndyVdrVersion>0.4.2-alpha</HyperledgerIndyVdrVersion>
         <MediatrExtensionsMicrosoftDependencyInjectionVersion>8.0.1</MediatrExtensionsMicrosoftDependencyInjectionVersion>
-        <MediatrVersion>8.0.2</MediatrVersion>
+        <MediatrVersion>12.4.0</MediatrVersion>
         <MicroElementsSwashbuckleFluentValidationVersion>4.0.0</MicroElementsSwashbuckleFluentValidationVersion>
         <MoqVersion>4.14.5</MoqVersion>
         <MultiformatsBaseVersion>2.0.2</MultiformatsBaseVersion>