Database updates (#144)

* start moving some database stuff around

* continue moving db stuff around

* more fiddling

* more updates

* and some more

* and yet more

* i broke SOMETHING but what, it's a mystery

* tidy up

* vendor ttlcache

* use ttlcache

* fix up some tests

* rename some stuff

* little reminder

* some more updates

1 files changed, 15 insertions, 13 deletions

diff --git a/internal/db/error.go b/internal/db/error.go
index 197c7bd68..c13bd78dd 100644
--- a/internal/db/error.go
+++ b/internal/db/error.go
@@ -18,16 +18,18 @@
 
 package db
 
-// ErrNoEntries is to be returned from the DB interface when no entries are found for a given query.
-type ErrNoEntries struct{}
-
-func (e ErrNoEntries) Error() string {
-	return "no entries"
-}
-
-// ErrAlreadyExists is to be returned from the DB interface when an entry already exists for a given query or its constraints.
-type ErrAlreadyExists struct{}
-
-func (e ErrAlreadyExists) Error() string {
-	return "already exists"
-}
+import "fmt"
+
+// Error denotes a database error.
+type Error error
+
+var (
+	// ErrNoEntries is returned when a caller expected an entry for a query, but none was found.
+	ErrNoEntries Error = fmt.Errorf("no entries")
+	// ErrMultipleEntries is returned when a caller expected ONE entry for a query, but multiples were found.
+	ErrMultipleEntries Error = fmt.Errorf("multiple entries")
+	// ErrAlreadyExists is returned when a caller tries to insert a database entry that already exists in the db.
+	ErrAlreadyExists Error = fmt.Errorf("already exists")
+	// ErrUnknown denotes an unknown database error.
+	ErrUnknown Error = fmt.Errorf("unknown error")
+)