Implement UTCTime decoding

Remove LocalTime decoding because it requires IO to convert from Postgres time.

test/Database/PostgreSQL/Opium/FromFieldSpec.hs

@@ -7,10 +7,11 @@ import Data.ByteString (ByteString)
 import Data.Time
   ( Day (..)
   , DiffTime
-  , LocalTime (..)
   , TimeOfDay (..)
+  , UTCTime (..)
   , fromGregorian
   , secondsToDiffTime
+  , timeOfDayToTime
   )
 import Data.Text (Text)
 import Database.PostgreSQL.LibPQ (Connection)
@@ -100,11 +101,11 @@ newtype ATimeOfDay = ATimeOfDay
 
 instance FromRow ATimeOfDay where
 
-newtype ALocalTime = ALocalTime
-  { localtime :: LocalTime
+newtype AUTCTime = AUTCTime
+  { utctime :: UTCTime
   } deriving (Eq, Generic, Show)
 
-instance FromRow ALocalTime where
+instance FromRow AUTCTime where
 
 newtype ARawField = ARawField
   { raw :: Opium.RawField ByteString
@@ -283,20 +284,20 @@ spec = do
       shouldFetch conn "SELECT time '00:01:00' AS timeofday" [ATimeOfDay $ TimeOfDay 0 1 0]
       shouldFetch conn "SELECT time '13:07:43' AS timeofday" [ATimeOfDay $ TimeOfDay 13 7 43]
 
-  describe "FromField LocalTime" $ do
-    it "Decodes timestamp" $ \conn -> do
-      let ts0 = LocalTime (fromGregorian 2023 10 2) (TimeOfDay 12 42 23)
-      shouldFetch conn "SELECT timestamp '2023-10-02 12:42:23' AS localtime" [ALocalTime ts0]
+  describe "FromField UTCTime" $ do
+    it "Decodes timestamp with timezone" $ \conn -> do
+      let ts0 = UTCTime (fromGregorian 2023 10 2) (timeOfDayToTime $ TimeOfDay 12 42 23)
+      shouldFetch conn "SELECT timestamp with time zone '2023-10-02 12:42:23' AS utctime" [AUTCTime ts0]
 
-      let ts1 = LocalTime (fromGregorian 294275 12 31) (TimeOfDay 23 59 59)
-      shouldFetch conn "SELECT timestamp '294275-12-31 23:59:59' AS localtime" [ALocalTime ts1]
+      let ts1 = UTCTime (fromGregorian 294275 12 31) (timeOfDayToTime $ TimeOfDay 23 59 59)
+      shouldFetch conn "SELECT timestamp with time zone '294275-12-31 23:59:59' AS utctime" [AUTCTime ts1]
 
-      let ts2 = LocalTime (fromGregorian 1 1 1) (TimeOfDay 0 0 0)
-      shouldFetch conn "SELECT timestamp '0001-01-01 00:00:00' AS localtime" [ALocalTime ts2]
+      let ts2 = UTCTime (fromGregorian 1 1 1) (timeOfDayToTime $ TimeOfDay 0 0 0)
+      shouldFetch conn "SELECT timestamp with time zone '0001-01-01 00:00:00' AS utctime" [AUTCTime ts2]
 
       -- See note at the FromField Day instance.
-      let ts3 = LocalTime (fromGregorian 0 2 29) (TimeOfDay 0 0 0)
-      shouldFetch conn "SELECT timestamp '0001-02-29 BC 00:00:00' AS localtime" [ALocalTime ts3]
+      let ts3 = UTCTime (fromGregorian 0 2 29) (timeOfDayToTime $ TimeOfDay 0 0 0)
+      shouldFetch conn "SELECT timestamp with time zone '0001-02-29 BC 00:00:00' AS utctime" [AUTCTime ts3]
 
   describe "FromField RawField" $ do
     it "Simply returns the bytestring without decoding it" $ \conn -> do