Unexported field because it's only used by the RPC APIs.

Started refactoring it to smaller functions for easier testing as well.

…o disk.

…ing.

Added unit tests as well.

…rom disk

Neither a pointer to a `GenesisDoc`, nor a slice of chunks.

- renamed `deleteGenesisChunks` to `Cleanup`
- better docs for test func
- fixed bug in `TestInitGenesisChunks`

Added parameter defining the chunk size so that the function doesn't create a
new buffer at every iteration of the loop.

These functions optionally accept a list of callbacks to execute at shutdown.
We use this feature to delete the genesis file's chunks from disk when the
server shuts down by passing a function that handles the deletion as a
parameter.
However, we could pass any other function we wish to execute at this stage.

The function now first checks for and deletes any existing chunks directory.
While a Node's graceful shutdown procedure deletes the genesis file chunks and
their enclosing directory, if the Node (or its RPC HTTP server) crashes, it's
possible that the genesis file chunks remain on disk and are present upon restart.

This is not necessarily a problem, but if the genesis file changes for any reason,
its chunks will also differ. Therefore, to be safe, we re-create the chunks from
scratch at startup.

…nks`.

From 755 to 700, i.e., only the owner can read, write, and execute.

Co-authored-by: Daniel <daniel.cason@informal.systems>

They now call `ServeWithShutdown` and `ServeTLSWithShutdown` with a nil
`shutdownTasks` list respectively.

They were calling `ServeWithShutdown` and `ServeTLSWithShutdown` with `nil` as
the `shutdownTasks` parameter. This is incorrect because it creates a list
containing one `nil` element. Consequently, when `ServeWithShutdown` and
`ServeTLSWithShutdown` will  execute the `for` loop over `shutdownTasks`, they will
encounter a `nil` pointer dereference, causing them to panic.