[meta] Feedback from migrating to 2.0 #906

I recently looked at migrating some existing code and had some thoughts about the migration (https://github.com/cdcent/cfa-evd-2025-interventions/pull/8)

Higher priority stuff:

• Split Property/IndexableProperty #909 impl_property! no longer works with f64 since it requires Hash, Eq, which is particularly a problem for structs that contain f64 (e.g., times for things)
• Make IxaError compatible with anyhow #908 IxaError isn't compatible with anyhow because it doesn't implement Send/Sync
• IxaError is, in practice, used quite a bit with the string variant: do we want to just add back support, or encourage people to move to defining their own errors/anyhow/something else? (we decided we will leave it but make it compatible with anyhow)
• Global property validation error should be less specific #910 Global property validation should probably take a more generic error (with Into etc.)

Other things that I thought are worth mentioning but maybe not immediately fixing

• accessing newtype property values with .0 is not ideal
• query_result_iterator + collect() does actually have use cases (particularly in reports) (we decided this was acceptable)