Description:

Related issue (if applicable): #1245

Mattermost supports parsing Native (http:// and https://) URLs as long as they conform to the following:

• https://mattermost.HOSTNAME/hooks/TOKEN
• http://mattermost.HOSTNAME/hooks/TOKEN

Rules for this to trigger:

• Must be part of mattermost subdomain

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• No lint errors (use flake8)
• 100% test coverage

Testing

Anyone can help test this source code as follows:

# Create a virtual environment to work in as follows:
python3 -m venv apprise

# Change into our new directory
cd apprise

# Activate our virtual environment
source bin/activate

# Install the branch
pip install git+https://github.com/caronc/apprise.git@1245-mattermost-native-url-support

# Test out the changes with the following command:
apprise -t "Test Title" -b "Test Message" \
  "https://mattermost.example.com/hooks/token-identifier-here"