Add Apprise notification integration

[caronc]

Description:

Added notification support for Apprise which drastically increases the number off notification services supported by Home Assistant. It also, unfortunately, provides some over-lap to services already supported.

Docs PR:

home-assistant/home-assistant.io#10451

Example entry for configuration.yaml (if applicable):

# Example configuration.yaml entry using Apprise URLs
notify:
  - name: NOTIFIER_NAME
    platform: apprise
    url: Define one ore more Apprise URLs

Configuration files can also be sourced (via another location on the same server, or a remote server. Apprise supports TEXT and YAML based configuration formats.

# Example configuration.yaml entry using Apprise Configuration URLs
notify:
  - name: NOTIFIER_NAME
    platform: apprise
    config: Define one ore more Apprise Configuration URLs

Apprise URLs loaded directly (using the url directive) or through configuration files are all appended together in one list. You can use both config and url in the same configuration if you wish.

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly. Update and include derived files by running python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt by running python3 -m script.gen_requirements_all.
• Untested files have been added to .coveragerc.

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[homeassistant]

Hi @caronc,

It seems you haven't yet signed a CLA. Please do so here.

Once you do that we will be able to review and accept this pull request.

Thanks!

[MartinHjelmare]

Please don't squash commits after review has started to make it easier for readers to track changes.

[MartinHjelmare]

Looks good!

Can be merged when build passes.

[caronc]

@MartinHjelmare Thanks for your help and patients in getting the testing working with me. I've updated the docs here in this PR: home-assistant/home-assistant.io#10451 to reference the TARGET reference i added.

Quick question though: In Apprise it's referenced as tagging. Do you prefer use of the target reference for consistency across all notification services? or is it okay that I use tag for consistency with Apprise? This is in reference to the actual sending of a notification here.

Thoughts?

[MartinHjelmare]

We have to use the target argument since that is what the service call may provide.

[MartinHjelmare]

Great!