feat: support save and load payload from file

[bj00rn]

Features

Save / Load payload from file

• Open file dialog to set topic payload from file when publishing
• Save value from payload to file
• Use cases
  • for convenience
  • saving binary files is not supported, files are generated with utf8 encoding

Certificate selection

• Move file operation to backend (not tested!)

Publish from file

Save payload to file

[bj00rn]

For some reason binary payloads do not get written with correct encoding

[thomasnordquist]

The front-end should probably not directly write to the filesystem.
This would block MQTT Explorer from becoming a web-app

[bj00rn]

moved file writing to backend, the read file operation is still in front atm. Same logic is in use for certificate selection

MQTT-Explorer/app/src/actions/ConnectionManager.ts

Line 84 in f25cab4

const data = await fsPromise.readFile(selectedFile)

. Better fix this too

[bj00rn]

@thomasnordquist moved certificate selection file read to backend too. I have not tested it though since i do not use certs

[thomasnordquist]

Just noticed, how is saving working.
Is the encoding thing still an issue?

[bj00rn]

Just noticed, how is saving working. Is the encoding thing still an issue?

Files are read/written in default utf-8 for now.

I experimented with opening payload from binary file but ran into problems since payload is encoded as string in reducer state from what I gather. To properly support binary payloads I think some refactoring needs to be done to support this.