plutus-pab: Adds Swagger support for web-server API (#3807)

* Add swagger support via openapi3

Co-authored-by: Danil Berestov <GooseDB@yandex.ru>

marlowe/marlowe.cabal

@@ -124,6 +124,7 @@ test-suite marlowe-test-long-running
         http-client -any,
         websockets -any,
         network -any,
+        openapi3 -any,
 
 test-suite marlowe-test
     import: lang
@@ -168,6 +169,7 @@ test-suite marlowe-test
         http-client -any,
         websockets -any,
         network -any,
+        openapi3
 
 -- | The PAB Specialised to the marlowe contract(s)
 executable marlowe-pab
@@ -192,5 +194,6 @@ executable marlowe-pab
     plutus-tx -any,
     purescript-bridge -any,
     marlowe -any,
+    openapi3,
   if !(impl(ghcjs) || os(ghcjs))
     build-depends: plutus-tx-plugin -any

marlowe/pab/MarloweContract.hs

@@ -11,6 +11,7 @@ module MarloweContract(MarloweContract(..), handlers) where
 import           Control.Monad.Freer                 (interpret)
 import           Data.Aeson                          (FromJSON, ToJSON)
 import           Data.Default                        (Default (def))
+import qualified Data.OpenApi                        as OpenApi
 import           Data.Text.Prettyprint.Doc           (Pretty (..), viaShow)
 import           GHC.Generics                        (Generic)
 import qualified Language.Marlowe.Client             as Marlowe
@@ -27,7 +28,7 @@ data MarloweContract =
     | WalletCompanion -- Wallet companion contract
     | MarloweFollower -- Follower contract
     deriving (Eq, Ord, Show, Read, Generic)
-    deriving anyclass (ToJSON, FromJSON)
+    deriving anyclass (ToJSON, FromJSON, OpenApi.ToSchema)
 
 instance Pretty MarloweContract where
     pretty = viaShow