Make method a configurable option (reportHTTP)

[NickBouwhuis]

Describe what you would like to achieve
I would like to be able to configure the HTTP method that the reportHTTP alert module uses. At the moment, this is hardcoded to be 'POST'. Making it incompatible with APIs that use other methods for messages (for example: Matrix uses 'PUT' requests for sending messages to rooms).

Describe why the current solution (if any) is not satisfactory
The current situation makes the module incompatible with APIs that do not use the 'POST' method.

Provide an example
For Matrix, the config.yml would look something like this:

  - file: reportHTTP
    channels:
      - hijack
      - newprefix
      - visibility
      - path
      - misconfiguration
      - rpki
      - roa
    params:
      templates: 
        default: '{"body": "${channel}: ${summary}", "msgtype": "m.text"}'
      headers:
      isTemplateJSON: true
      showPaths: 0
      method: 'PUT'
      hooks:
        default: https://HOMESERVER/_matrix/client/v3/rooms/CHANNELID/send/m.room.message/?access_token=TOKEN

Your information
By day:
Nick Bouwhuis
Speakup B.V.
AS49627

By night:
Nick Bouwhuis
AS202585

[massimocandela]

Hi @NickBouwhuis,

This can be done easily, I'll give it a look asap.

[massimocandela]

This is done and it will go out with the next release.
However, I see that you are using Matrix, which was requested also by #977

It would be nice if you could do a pull request (in branch dev) containing a documentation snippet of a working JSON template for Matrix. For example, you can follow what has been done here. Thanks.