python: add simple test for AWS lambda

made space for other serverless frameworks in the directory `serverless`

python/ql/test/library-tests/frameworks/serverless/RemoteFlowSourceTest.expected

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+failures
+testFailures

python/ql/test/library-tests/frameworks/serverless/RemoteFlowSourceTest.ql

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+import python
+import TestUtilities.InlineExpectationsTest
+
+private module RemoteFlowTest implements TestSig {
+  private import semmle.python.dataflow.new.RemoteFlowSources
+  private import semmle.python.dataflow.new.internal.PrintNode
+
+  string getARelevantTag() { result = "remoteFlow" }
+
+  predicate hasActualResult(Location location, string element, string tag, string value) {
+    exists(RemoteFlowSource source |
+      location = source.getLocation() and
+      tag = "remoteFlow" and
+      value = prettyNode(source) and
+      element = source.toString()
+    )
+  }
+}
+
+import MakeTest<RemoteFlowTest>

python/ql/test/library-tests/frameworks/serverless/aws_lambda/function/extra_lambdas.py

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+def handler1(event, context): # $ MISSING: remoteFlow=event, remoteFlow=context
+    return "Hello World!"
+
+def handler2(event, context): # $ MISSING: remoteFlow=event, remoteFlow=context
+    return "Hello World!"

python/ql/test/library-tests/frameworks/serverless/aws_lambda/function/lambda_function.py

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+def lambda_handler(event, context): # $ MISSING: remoteFlow=event, remoteFlow=context
+    return "OK"

python/ql/test/library-tests/frameworks/serverless/aws_lambda/template.yml

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+# inspired by https://github.com/awsdocs/aws-lambda-developer-guide/blob/main/sample-apps/blank-python/template.yml
+# but we have added extra handlers
+AWSTemplateFormatVersion: '2010-09-09'
+Transform: 'AWS::Serverless-2016-10-31'
+Description: An AWS Lambda application that calls the Lambda API.
+Resources:
+  function:
+    Type: AWS::Serverless::Function
+    Properties:
+      Handler: lambda_function.lambda_handler
+      Runtime: python3.8
+      CodeUri: function/.
+      Description: Call the AWS Lambda API
+      Timeout: 10
+      # Function's execution role
+      Policies:
+        - AWSLambdaBasicExecutionRole
+        - AWSLambda_ReadOnlyAccess
+        - AWSXrayWriteOnlyAccess
+      Tracing: Active
+      Layers:
+        - !Ref libs
+  function:
+    Type: AWS::Serverless::Function
+    Properties:
+      Handler: extra_lambdas.handler1
+      Runtime: python3.8
+      CodeUri: function/.
+      Description: Call the AWS Lambda API
+      Timeout: 10
+      # Function's execution role
+      Policies:
+        - AWSLambdaBasicExecutionRole
+        - AWSLambda_ReadOnlyAccess
+        - AWSXrayWriteOnlyAccess
+      Tracing: Active
+      Layers:
+        - !Ref libs
+  function:
+    Type: AWS::Serverless::Function
+    Properties:
+      Handler: extra_lambdas.handler2
+      Runtime: python3.8
+      CodeUri: function/.
+      Description: Call the AWS Lambda API
+      Timeout: 10
+      # Function's execution role
+      Policies:
+        - AWSLambdaBasicExecutionRole
+        - AWSLambda_ReadOnlyAccess
+        - AWSXrayWriteOnlyAccess
+      Tracing: Active
+      Layers:
+        - !Ref libs
+  libs:
+    Type: AWS::Serverless::LayerVersion
+    Properties:
+      LayerName: blank-python-lib
+      Description: Dependencies for the blank-python sample app.
+      ContentUri: package/.
+      CompatibleRuntimes:
+        - python3.8

python/ql/test/library-tests/frameworks/serverless/options

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+semmle-extractor-options: -R .