Add Ability to Define Variables in Frigate Config File

[alexlmiller]

Given how much repeated text there is in my config file, it would be great to be able to define variables in the config that can be re-used across various places. Obviously there are environmental variables but those are limited in which are parsed.

My particular use case is with the generative ai feature where (best I can tell from the docs), if you use camera or object specific prompts, that prompt stands entirely alone, which means if you have some kind of context that you want used on all responses (eg, communication/writing style), you need to update that on every single prompt in your config file (which could be many). It would be great to be able to define a variable (eg: PROMPT_WRITING_STYLE or PROMPT_GARAGE_CAM_CONTEXT) that I can use in all the specific prompts to share the common language while only needing to update in one mplace.