Add outputs to pygeoapi processes in core (#1902)

* Add outputs to OAProc

* Use **kwargs

cc #1899

* Use named function arguments

Author: webb-ben

pygeoapi/process/echo.py

@@ -115,7 +115,7 @@ def __init__(self, processor_def):
 
         super().__init__(processor_def, PROCESS_METADATA)
 
-    def execute(self, data):
+    def execute(self, data, outputs=None):
 
         mimetype = 'application/json'
 

pygeoapi/process/shapely_functions.py

@@ -249,7 +249,7 @@ def __init__(self, processor_def):
         self.supported_formats = [fmt.value for fmt in SupportedFormats]
         super().__init__(processor_def, PROCESS_METADATA)
 
-    def execute(self, data) -> Tuple[str, Dict[str, Any]]:
+    def execute(self, data, outputs=None) -> Tuple[str, Dict[str, Any]]:
         mimetype = "application/json"
         operation = data.get("operation")
         output_format = data.get("output_format")