ESPTime::strptime alternate formats

[rcswift]

Component name

ESPTime

Link to component documentation on our website

https://api-docs.esphome.io/structesphome_1_1_e_s_p_time#a693cbf767073ca0a9529951963805388

Describe the enhancement

Currently the ESPTime::strptime method is limited to a select few formats for parsing timestamps.

It would be helpful to expand support to include an override with a format parameter, as with the standard C strftime, for parsing arbitrary timestamp formats.

If for whatever reason that is impractical, it would be helpful to expand support to include the full ISO8601 timestamp format (e.g. 2026-03-09T20:50:00+00:00).

Use cases

When retrieving weather forecast data from HomeAssistant, the datetime of the forecast is provided as an ISO8601 format string:

weather.forecast:
  forecast:
    - datetime: "2026-03-09T20:50:00+00:00"
      precipitation_probability: 0
      condition: clear-night
      temperature: null
      templow: 4
    [...]

Anything else?

No response