make initialization of inactive job possible

This commit adds to ability to define a job in a config
as being inactive when initializing. This can be useful when
you want to define certain jobs that you want to set active
in the app at runtime without the need to configure the whole
job at runtime.

lib/quantum.ex

@@ -13,6 +13,7 @@ defmodule Quantum do
     timeout: 5_000,
     schedule: nil,
     overlap: true,
+    state: :active,
     timezone: :utc,
     run_strategy: {Random, :cluster},
     debug_logging: true

lib/quantum/job.ex

@@ -63,13 +63,15 @@ defmodule Quantum.Job do
          overlap when is_boolean(overlap) <- Keyword.fetch!(config, :overlap),
          timezone when timezone == :utc or is_binary(timezone) <-
            Keyword.fetch!(config, :timezone),
+         state when is_atom(state) <- Keyword.fetch!(config, :state),
          schedule <- Keyword.get(config, :schedule) do
       %__MODULE__{
         name: name,
         overlap: Keyword.fetch!(config, :overlap),
         timezone: Keyword.fetch!(config, :timezone),
         run_strategy: run_strategy,
-        schedule: schedule
+        schedule: schedule,
+        state: state
       }
     end
   end

test/quantum/job_test.exs

@@ -20,4 +20,11 @@ defmodule Quantum.JobTest do
 
     assert %Job{schedule: ^schedule, overlap: false} = Job.new(configs)
   end
+
+  test "is is possible to initialize a job as inactive" do
+    configs = Scheduler.config(schedule: "*/7", overlap: false, state: :inactive)
+    schedule = ~e[*/7]
+
+    assert %Job{schedule: ^schedule, overlap: false, state: :inactive} = Job.new(configs)
+  end
 end