Added support for upload of remote or local files to slack

[simaosimao]

Description:

The notify.slack platform currently supports sending text messages and structured message attachments (see chat.postMessage). This PR's intention is to add support for uploading files either from the local machine/server or from a remote url (See files.upload).

I am using this feature to post security camera still pictures to a slack channel when certain events occur. Might be useful to others...?

Example: Post file or image by url

Use the following service data for notify.slack in order to directly post a remote file:

{
  "message":"Message that will be added as a comment to the file, e.g. photo.",
  "title":"Title of the file, e.g. photo",
  "data":{
    "file":{
      "url":"http://<url to file, photo, security camera etc>",
      "username":"optional user, if necessary",
      "password":"optional password, if necessary",
      "auth":"digest"
    }
  }
}

"auth":"digest" is optional, too. If omitted basic authentication is used.

Example: Post file or image by local path

Use the following service data for notify.slack in order to post local file

{
  "message":"Message that will be added as a comment to the file, e.g. photo.",
  "title":"Title of the file, e.g. photo",
  "data":{
    "file":{
      "path":"/path/to/file.ext"
    }
  }
}

Sidenote

This is my first PR (at all) and I am no python developer. I tried to familiarize with applying rules and conventions, running tests etc. Still I might have missed something ... please excuse any mistakes.

Pull request in home-assistant.github.io with documentation (if applicable): home-assistant/home-assistant.io#2949

Checklist:

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

• Documentation added/updated in home-assistant.github.io

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

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass

[mention-bot]

@simaosimao, thanks for your PR! By analyzing the history of the files in this pull request, we identified @fabaff, @Khabi and @balloob to be potential reviewers.

[homeassistant]

Hi @simaosimao,

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!

[pvizeli]

I'm not sure if we should make a helper function for fileload

[pvizeli]

You need check the path with hass.config.is_allowed_path

[simaosimao]

Hi @pvizeli, thanks for your feedback! Using suggested check now. Had to move the load_file method into the SlackNotificationService class in order to keep a reference to is_allowed_path.

Also had a look at the telegram bot which has a similar method to load a file. We might extract those to a helper function as you mentioned above in a follow up issue 😉

Opened #8291, as is_allowed_path could be further secured.

[balloob]

Awesome 🎉 🌮 🐬

[simaosimao]

Thx 😄