[INS-1786] WebSocket headers tab

[jackkav]

Motivation: Send custom headers

Highlights

• adds header tab to request pane
• extends RequestHeaderEditor component to support WebSocketRequest and readOnly headers
• adds outgoing header logging to ws smoke test server

Todo

• add headers tab
• init model with some defaults
• get everything rendering consistently
• wire up bulk editor toggle
• fix tab/button/bar css alignment
• make default header values accurate
• disable editing while connected

Possible future work

• nunjucks rendering, not done in message tab yet, better tackled at the same time
• prettify event log view / payload
• add upgrade event, response status code/message, headers and handle set-cookies
• add outgoing headers to request object?

Notes:

Since the websocket client doesn't expose the request headers which are actually sent to the server.
We can either construct it or perhaps redirect it through a local server to capture, but for now we show the headers as read only in the headers tab.

[filfreire]

⚠️ Headers related Problems:

• There's a border in the bottom when you add a ton of headers. On HTTP requests this is where you'd keep the bulk edit button, not sure if we should remove that border, or leave it as is.
  

This is how it looks like for HTTP requests:

❓ Not sure and possibly out of scope:

• Do we need to support empty value headers (e.g. only key is defined)
• Do we need to support some sort of header "array" - e.g. where if you define the same key a handful of times, it would be picked up as an array - some folks talk about this for query parameters in HTTP requests

🧨 Non headers related problems we will need to tackle at some point:

• switching back and forth from message and headers tab - loses the contents of the message tab
• create a new WS request reuses URL from another WS request that is in context
• switching tabs between WS request in some cases also ports over the WS URL into the request you switched into
• moving websocket requests in the tree view doesn't work properly, most times you can't move them, and you can only move one inside a folder

We'll need to capture these last ones somewhere.

[jackkav]

@filfreire Thanks!

Do we need to support empty value headers (e.g. only key is defined)

we do not currently allow that in HTTP requests, see parse-header-strings.ts#L89

Do we need to support some sort of header "array"

out of scope, feel free to create an investigation ticket

switching back and forth from message and headers tab - loses the contents of the message tab

out of scope, in order to avoid migrating the data model, message persistence is subject to change

create a new WS request reuses URL

not introduced by this PR but fixed in this PR

moving websocket requests in the tree view doesn't work properly

not introduced by this PR, feel free to create a ticket.