Use strum macros and serde to automatically deserialize enums from strings

Example
```
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
pub enum TriggerType {
IMMEDIATE,
DELAYED,
CRON,
}
```

Start by locating the TriggerType enum and its current serialization derives; no file or test is named in the issue. Check how string deserialization is currently handled, then add coverage for the enum values shown in the example and verify that the expected strings deserialize successfully.

Written by the indexing model from the issue text.