Changes in Fluid Framework v2.0.0-internal.6.1.0

Removed TelemetryNullLogger class is again exported from @fluidframework/telemetry-utils

The TelemetryNullLogger class has been brought back to ease the transition to 2.0.0-internal.6.x but is still deprecated and will be removed in 2.0.0-internal.7.0.0.

For internal use within the FluidFramework codebase, use createChildLogger() with no arguments instead. For external consumers we recommend writing a trivial implementation of ITelemetryBaseLogger (from the @fluidframework/core-interfaces package) where the send() method does nothing and using that.

Deprecates DeltaManagerProxyBase

DeltaManagerProxyBase is only used internally in FluidFramework code and will no longer be exported in a future release. No replacement API is intended for external consumers.