transfer of realm features to astarte_data_access

[shinnokdisengir]

In order to manage the database also from applications external to astarte, such as the various tests and products like astarte_dev_tool, the commands needed to manage the realms from the astarte_housekeeping to astarte_data_access

[Annopaolo]

The function call with many parameters inside a with inside a fn inside a case makes somewhat difficult to follow where the :ok/{:error, reason} below do come from.
I would suggest two changes:

• Since we're inside a library, it is reasonable to think that the library user has more context regarding realm creation, so the caller of create_realm can decide whether to log or not. Removing the warning would also remove the need for case. This would be somewhat inconsistent with the rest of the library (we have lots of logs!) but more in line with the standard practice.
• Generating astarte_keyspace_name and replication_map_str can be moved inside the with block in do_create_realm, as they're needed in every call.
  Essentially, this would turn into

Suggested change

	case XandraUtils.run(realm_name, fn conn, keyspace_name ->
	astarte_keyspace_name = XandraUtils.build_keyspace_name!("astarte")
	with :ok <- check_replication(conn, replication),
	{:ok, replication_map_str} <- build_replication_map_str(replication) do
	do_create_realm(
	conn,
	keyspace_name,
	astarte_keyspace_name,
	realm_name,
	replication_map_str,
	max_retention,
	public_key_pem,
	device_registration_limit,
	realm_schema_version
	)
	end
	end) do
	:ok ->
	:ok
	{:error, reason} ->
	Logger.warning("Cannot create realm: #{inspect(reason)}.",
	tag: "realm_creation_failed",
	realm: realm_name
	)
	{:error, reason}
	end
	end
	XandraUtils.run(
	realm_name,
	&do_create_realm(
	&1,
	realm_name,
	replication,
	max_retention,
	public_key_pem,
	device_registration_limit,
	realm_schema_version
	)
	)
	end

[Annopaolo]

The above suggestion on error logging applies also here:

Suggested change

	case XandraUtils.run(realm_name, fn conn, keyspace_name ->
	astarte_keyspace_name = XandraUtils.build_keyspace_name!("astarte")
	do_delete_realm(conn, keyspace_name, astarte_keyspace_name, realm_name)
	end) do
	:ok ->
	:ok
	{:error, reason} ->
	Logger.warning("Cannot delete realm: #{inspect(reason)}.",
	tag: "realm_deletion_failed",
	realm: realm_name
	)
	{:error, reason}
	end
	XandraUtils.run(realm_name, fn conn, keyspace_name ->
	astarte_keyspace_name = XandraUtils.build_keyspace_name!("astarte")
	do_delete_realm(conn, keyspace_name, astarte_keyspace_name, realm_name)
	end)

Note that it is not mandatory, but we can decide for one option or the other in the whole PR (I suggest to remove logs).