Prevent breaking blocks beneath pipes or the flagpole

[WilliamFr0g]

People commonly use bricks below exit pipes from underground levels, which may be destroyed, rendering the level uncompletable. This is no fun and really doesn't need to happen at all. Additionally, flagpoles are commonly placed on hard blocks, which can also be destroyed, leaving the pole floating. This is wonky and similarly doesn't need to be allowed.

[Alexis0159]

The hard block can be used as a solid block, or a custom property of the flagpole can be used by adding properties that prevent the block from being destroyed. It would be feasible for the flagpole to be an entity.