<!--- Verify first that your issue is not already reported on GitHub -->
<!--- Also test if the latest release and devel branch are affected too -->
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##### SUMMARY
<!--- Explain the problem briefly below -->

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
<!--- Write the short name of the module, plugin, task or feature below, use your best guess if unsure -->

postgresql_slot, postgresql_user

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.8.3
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['~/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python3.7/site-packages/ansible
  executable location = /usr/bin/ansible
  python version = 3.7.4 (default, Jul 16 2019, 07:12:58) [GCC 9.1.0]
```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->
archlinux latest

##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml
- postgresql_user:
    name: user1
    password: password
  become: true
  become_user: postgres

- postgresql_slot:
    name: slot1
  become: true
  become_user: postgres
```

<!--- HINT: You can paste gist.github.com links for larger files -->

##### EXPECTED RESULTS
<!--- Describe what you expected to happen when running the steps above -->
Consistent warnings. Either both postgresql_user and postgresql_slot should give a warning or neither should.

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->
postgresql_slot gives warning "[WARNING]: Database name has not been passed, used default database to connect to." but postgresql_user doesn't, even though both of them have not specified a database.
description:
    - Switch to session_role after connecting. The specified session_role must
      be a role that the current login_user is a member of.
    - Permissions checking for SQL commands is carried out as though
      the session_role were the one that had logged in originally.
    type: str
  db:
    description:
    - Name of database to connect to and run queries against.
    type: str
    aliases:
    - login_db
notes:
- I(state=absent) and I(state=present) (the second one if the tablespace doesn't exist) do not
  support check mode because the corresponding PostgreSQL DROP and CREATE TABLESPACE commands
  can not be run inside the transaction block.
author:
- Flavien Chantelot (@Dorn-)
- Antoine Levy-Lambert (@antoinell)
- Andrew Klychkov (@Andersson007)
extends_documentation_fragment: postgres
'''
EXAMPLES = r'''
- name: Create a new tablespace called acme and set bob as an its owner
  postgresql_tablespace:
    name: acme
    owner: bob
    location: /data/foo
- name: Create a new tablespace called bar with tablespace options
  postgresql_tablespace: