Add option missing to passwordstore lookup (#2500)

Add ability to ignore error on missing pass file to allow processing the
output further via another filters (mainly the default filter) without
updating the pass file itself.

It also contains the option to create the pass file, like the option
create=true does.

Finally, it also allows to issue a warning only, if the pass file is not
found.

tests/integration/targets/lookup_passwordstore/tasks/tests.yml

@@ -61,6 +61,37 @@
     that:
       - readpass == newpass
 
+- name: Create a password using missing=create
+  set_fact:
+    newpass: "{{ lookup('community.general.passwordstore', 'test-missing-create missing=create length=8') }}"
+
+- name: Fetch password from an existing file
+  set_fact:
+    readpass: "{{ lookup('community.general.passwordstore', 'test-missing-create') }}"
+
+- name: Verify password
+  assert:
+    that:
+      - readpass == newpass
+
+- name: Fetch password from existing file using missing=empty
+  set_fact:
+    readpass: "{{ lookup('community.general.passwordstore', 'test-missing-create missing=empty') }}"
+
+- name: Verify password
+  assert:
+    that:
+      - readpass == newpass
+
+- name: Fetch password from non-existing file using missing=empty
+  set_fact:
+    readpass: "{{ query('community.general.passwordstore', 'test-missing-pass missing=empty') }}"
+
+- name: Verify password
+  assert:
+    that:
+      - readpass == [ none ]
+
 # As inserting multiline passwords on the commandline would require something
 # like expect, simply create it by using default gpg on a file with the correct
 # structure.