Add thiserror instead of exposing eyre anonymous errors

The change here is to make it easier for the consumer to debug the api.
Such that they can `match` on individual errors instead of having to
parse text.

eyre is convenient, but mostly from a consumers perspective

Cargo.lock

@@ -334,6 +334,7 @@ dependencies = [
  "sha2",
  "tar",
  "tempfile",
+ "thiserror",
  "tokio",
  "tracing",
  "tracing-subscriber",
@@ -352,6 +353,7 @@ dependencies = [
  "rand",
  "serde",
  "serde_json",
+ "thiserror",
  "tokio",
  "tracing",
  "tracing-subscriber",