add multiple device should cache login info in memory

[wuwentao]

Device type and model (or SN)

none

The description of new feature

in this chanages: https://github.com/wuwentao/midea_ac_lan/commit/1f56e69b7ebcabdf634a8eb14c44f44dec4470e7 we have removed write username/password to local json file, and not save username/password in local disk.

it caused a small issue: if user have more than 5-10+ device to be add, they should add each device and input login username/password every time. we can cache it in memory and not write to file, can be done in future

[chemelli74]

I investigate with the core Team and this is not allowed at the time writing.

[wuwentao]

I investigate with the core Team and this is not allowed at the time writing.

understand, username/password is sensitive data, HA core may not allow to cache it. we can delay it, not a urgent requirement.