Update OpenFga.Sdk to version 0.8.0

[carstenkind]

Fix package version conflicts with OpenFGA SDK 0.8.0

Changes Made

• Updated Microsoft.Extensions.Http package references from 8.0.0/9.0.0 to 9.0.9 to resolve package downgrade conflicts
• Updated BatchCheckResponse type references to ClientBatchCheckClientResponse to match OpenFGA SDK 0.8.0 API changes

Fixes

• Resolves NU1605 package downgrade warnings during dotnet restore
• Fixes compilation errors related to missing BatchCheckResponse type

Testing

• All projects now build successfully
• Package restore completes without errors

[Hawxy]

Thanks!