Turn large ntfy messages into a attachments

[caronc]

Description:

Related issue (if applicable): n/a

It was requested on Discord to avoid passing along large ntfy messages since the upstream blocks them. However to simulate what the ntfy cli does, it takes large body/title content and creates an attachment from it. It specifically targets the JSON body too large Error message the ntfy server sends back if your message is to large for it.

The largest feature introduced into this PR is the introduction of a memory based Attachment file. @joergschultzelutter may appreciate this as he asked for it earlier.

from apprise.attachment.memory import AttachMemory

# Initialize
attach = AttachMemory(content="attachment-content-here")

# Now it behaves like other attachments in apprise and is transparent to
# alike calls that utilize `http` and `file` based ones.  

The use case for the memory attachment is so you don't have to write a temporary file to disk and then reference the content as an AttachFile

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@attach-large-ntfy-message

# Test out the changes with the following command:
apprise -t "Test Title" -b "Test Message" ntfy://topic

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.28%. Comparing base (e289279) to head (d3a2d7b).

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Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1136   +/-   ##
=======================================
  Coverage   99.28%   99.28%           
=======================================
  Files         140      141    +1     
  Lines       18234    18331   +97     
  Branches     3729     3750   +21     
=======================================
+ Hits        18103    18200   +97     
  Misses        121      121           
  Partials       10       10           

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[joergschultzelutter]

Definitely appreciated as your code enhancement removes my need for juggling with temporary files.

Cheers @caronc - and: thank you!
Joerg