Edit RealmManagement api :use keyspace name instead of realm in queries

Currently Astarte instances are not allowd to share the same database due to a conflict in namespaces
resolution (eg. two realms with same name in different astarte instances now share the same kespace,
that's not good)

This commit introduce univoque mapping between the pair <Astarte instance id, realm name>
and keyspace name (see also  astarte-platform/astarte_core#105), this way even
with the same name, realms do not share the same keyspace.
Also, the env var `ASTARTE_INSTANCE_ID`, defaulting to `""` has been added to
maintain backward compatibility.

Trivially change all queries to the database to reflect this change, both in `lib` and `tests`.

Signed-off-by: Eddy Babetto <eddy.babetto@secomind.com>

apps/astarte_realm_management_api/mix.lock

@@ -1,9 +1,9 @@
 %{
   "amqp": {:hex, :amqp, "3.3.0", "056d9f4bac96c3ab5a904b321e70e78b91ba594766a1fc2f32afd9c016d9f43b", [:mix], [{:amqp_client, "~> 3.9", [hex: :amqp_client, repo: "hexpm", optional: false]}], "hexpm", "8d3ae139d2646c630d674a1b8d68c7f85134f9e8b2a1c3dd5621616994b10a8b"},
   "amqp_client": {:hex, :amqp_client, "3.12.10", "dcc0d5d0037fa2b486c6eb8b52695503765b96f919e38ca864a7b300b829742d", [:make, :rebar3], [{:credentials_obfuscation, "3.4.0", [hex: :credentials_obfuscation, repo: "hexpm", optional: false]}, {:rabbit_common, "3.12.10", [hex: :rabbit_common, repo: "hexpm", optional: false]}], "hexpm", "16a23959899a82d9c2534ed1dcf1fa281d3b660fb7f78426b880647f0a53731f"},
-  "astarte_core": {:git, "https://github.com/astarte-platform/astarte_core.git", "685ca10c7a07cc9806f2c6fc7ec2ed1b4d23cbec", []},
-  "astarte_rpc": {:git, "https://github.com/astarte-platform/astarte_rpc.git", "9b20db0077d99461f11a380e964689465aa566fa", []},
-  "castore": {:hex, :castore, "0.1.22", "4127549e411bedd012ca3a308dede574f43819fe9394254ca55ab4895abfa1a2", [:mix], [], "hexpm", "c17576df47eb5aa1ee40cc4134316a99f5cad3e215d5c77b8dd3cfef12a22cac"},
+  "astarte_core": {:git, "https://github.com/astarte-platform/astarte_core.git", "dc964b7d9b3a3a4e20127b763705d9e53bd88890", []},
+  "astarte_rpc": {:git, "https://github.com/astarte-platform/astarte_rpc.git", "c0d77760fb12256a23a2d00e1a119496a089fa9d", []},
+  "castore": {:hex, :castore, "1.0.7", "b651241514e5f6956028147fe6637f7ac13802537e895a724f90bf3e36ddd1dd", [:mix], [], "hexpm", "da7785a4b0d2a021cd1292a60875a784b6caef71e76bf4917bdee1f390455cf5"},
   "certifi": {:hex, :certifi, "2.9.0", "6f2a475689dd47f19fb74334859d460a2dc4e3252a3324bd2111b8f0429e7e21", [:rebar3], [], "hexpm", "266da46bdb06d6c6d35fde799bcb28d36d985d424ad7c08b5bb48f5b5cdd4641"},
   "cors_plug": {:hex, :cors_plug, "2.0.3", "316f806d10316e6d10f09473f19052d20ba0a0ce2a1d910ddf57d663dac402ae", [:mix], [{:plug, "~> 1.8", [hex: :plug, repo: "hexpm", optional: false]}], "hexpm", "ee4ae1418e6ce117fc42c2ba3e6cbdca4e95ecd2fe59a05ec6884ca16d469aea"},
   "cowboy": {:hex, :cowboy, "2.10.0", "ff9ffeff91dae4ae270dd975642997afe2a1179d94b1887863e43f681a203e26", [:make, :rebar3], [{:cowlib, "2.12.1", [hex: :cowlib, repo: "hexpm", optional: false]}, {:ranch, "1.8.0", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm", "3afdccb7183cc6f143cb14d3cf51fa00e53db9ec80cdcd525482f5e99bc41d6b"},