Allow preserving WiFi credentials entered with captive_portal

[kuba2k2]

What does this implement/fix?

This PR allows the user to preserve the WiFi credentials, that were entered using captive_portal, over subsequent OTA updates. I think this may be a useful feature, given that guides like Sharing ESPHome devices exist, and the recent addition of a "factory reset" component. When using keep_user_credentials, the user can freely reconfigure a device to a different network in a WiFiManager-like manner, whether it's a DIY, tuya-converted, or vendor-supplied ESPHome device.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other

Pull request in esphome-docs with documentation (if applicable): esphome/esphome-docs#2301

Test Environment

• ESP32
• ESP32 IDF
• ESP8266
• LibreTuya port

Example entry for config.yaml:

# Example config.yaml
wifi:
  keep_user_credentials: true
  # ssid: "my_ssid_unused"
  # password: "1234"
  ap:
    password: "ESPHome123"

Checklist:

• The code change is tested and works locally.
• Tests have been added to verify that the new code works (under tests/ folder).
• Documentation added/updated in esphome-docs.

[jesserockz]

The issue here is that if you flash a YAML over top that has credentials "built in", they wont work unless you remove the keep_user_credentials: true so there needs to be some validation on the config there to prevent both at the same time.

[kuba2k2]

Right, that's a good point! I'll refactor that tomorrow.

EDIT: Is a runtime (or compile-time) verification also required (in the C++ code)?

[kuba2k2]

Okay, the option is now incompatible with either ssid, password or networks.

Failed config

wifi: [source .\aubess-4b1-03h4-01.yml:35]

  WiFi credentials cannot be used together with keep_user_credentials.
  keep_user_credentials: True
  ssid: 127.0.0.1
  ap:
    password: FallbackApPassword

The corresponding esphome-docs PR has also been updated to make that clear.

[probot-esphome]

Hey there @OttoWinter, mind taking a look at this pull request as it has been labeled with an integration (captive_portal) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[jesserockz]

Feels weird the way this works, but its fine.
Just a rename of the define below please.