Always send formatted content

[langleyd]

Fixes #1999

I can understand the rational behind why the code that removes formatted_body for non-RTE mode might have been added but whether we send 'formatted_body' should not be tied to the RTE, we should always send it(e.g. the web client sends it even on the legacy client which is markdown based, as do legacy mobile markdown clients).

It is the preferred field for clients that support displaying rich content, whereas body field is a plain text representation of what is in formatted_body and can be used for clients that don't support displaying rich content.

formatted_body is required for mentions to work and render correctly in the timeline, hence the bug.

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@@             Coverage Diff             @@
##           develop    #2141      +/-   ##
===========================================
- Coverage    72.00%   71.91%   -0.09%     
===========================================
  Files          511      511              
  Lines        34722    34721       -1     
  Branches     16673    16673              
===========================================
- Hits         25001    24971      -30     
- Misses        9105     9137      +32     
+ Partials       616      613       -3     

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[pixlwave]

I can understand the rational behind why the code that removes formatted_body for non-RTE mode might have been added but whether we send 'formatted_body' should not be tied to the RTE, we should always send it(e.g. the web client sends it even on the legacy client which is markdown based, as do legacy mobile markdown clients).

I don't think its that simple. We always send the formatted_body when it isn't included, but Rust builds it from the Markdown in the body and attaches it within the SDK. So with this change, sending a message with Markdown will no longer work unless the RTE is updated to parse it first.

[pixlwave]

An example, this is from develop:

"content": {
    "body": "This is **bold**.",
    "format": "org.matrix.custom.html",
    "formatted_body": "<p>This is <strong>bold</strong>.</p>\n",
    "m.mentions": {},
    "msgtype": "m.text"
},

And this is with the changes:

"content": {
    "body": "This is **bold**.",
    "format": "org.matrix.custom.html",
    "formatted_body": "This is **bold**.",
    "m.mentions": {},
    "msgtype": "m.text"
}

Presumably we either need to fix the pills some other way or enable MD input support in the RTE.

[stefanceriu]

Handled in #2246