## Objective
Add a way to stream BRP requests when the data changes.
## Solution
#### BRP Side (reusable for other transports)
Add a new method handler type that returns a optional value. This
handler is run in update and if a value is returned it will be sent on
the message channel. Custom watching handlers can be added with
`RemotePlugin::with_watching_method`.
#### HTTP Side
If a request comes in with `+watch` in the method, it will respond with
`text/event-stream` rather than a single response.
## Testing
I tested with the podman HTTP client. This client has good support for
SSE's if you want to test it too.
## Parts I want some opinions on
- For separating watching methods I chose to add a `+watch` suffix to
the end kind of like `content-type` headers. A get would be
`bevy/get+watch`.
- Should watching methods send an initial response with everything or
only respond when a change happens? Currently the later is what happens.
## Future work
- The `bevy/query` method would also benefit from this but that
condition will be quite complex so I will leave that to later.
---------
Co-authored-by: Zachary Harrold <zac@harrold.com.au>
# Objective
- fulfill the needs presented in this issue, which requires the ability
to set custom HTTP headers for responses in the Bevy Remote Protocol
server. #15551
## Solution
- Created a `Headers` struct to store custom HTTP headers as key-value
pairs.
- Added a `headers` field to the `RemoteHttpPlugin` struct.
- Implemented a `with_headers` method in `RemoteHttpPlugin` to allow
users to set custom headers.
- Passed the headers into the processing chain.
## Testing
- I added cors_headers in example/remote/server.rs and tested it with a
static html
[file](https://github.com/spacemen0/bevy/blob/test_file/test.html)
---
## Objective
Closes#15408 (somewhat)
## Solution
- Moved the existing HTTP transport to its own module with its own
plugin (`RemoteHttpPlugin`) (disabled on WASM)
- Swapped out the `smol` crate for the smaller crates it re-exports to
make it easier to keep out non-wasm code (HTTP transport needs
`async-io` which can't build on WASM)
- Added a new public `BrpSender` resource holding the matching sender
for the `BrpReceiver`' (formally `BrpMailbox`). This allows other crates
to send `BrpMessage`'s to the "mailbox".
## Testing
TODO
---------
Co-authored-by: Matty <weatherleymatthew@gmail.com>
