Allow OperatorType to be a list such that one API can map to multiple operations (#166)

Allow OperatorType to be a list such that one API can map to multiple operations. 
This is required in certain cases where the same API call maps to both Create and Update operations such as `RegisterScalableTarget` and `PutScalingPolicy`

[Link to ApplicationAutoscaling PR with the related change](aws-controllers-k8s/applicationautoscaling-controller#27)
Note: This change will require all other services to update their generator configs as well. 

Issue #, if available:
aws-controllers-k8s/community#867

### Description of changes:
The `getOpTypeAndResourceName` method handles each of the following cases same as before in addition to the new case 5- 
1.  the cfg itself is nil
2.  cfg is not nil but opId is not in the cfg
3.  cfg is not nil, the opID is in the cfg but the opType is not specified
  ```
  operations:
    DescribeScalableTargets:
    primary_identifier_field_name: ResourceID
  ```
4. One API -> one operations
```
operations:
  PutScalingPolicy:
    operation_type: 
    - Create
  ```
5. One API -> multiple operations
```
operations:
  PutScalingPolicy:
    operation_type: 
    - Create
    - Update
  ```
### Testing
- I tested by generating the controller code for both applicationAutoscaling and the SageMaker repos. 
- The unit tests pass as is. 

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Author: mbaijal

pkg/generate/config/operation.go

@@ -14,11 +14,17 @@
 package config
 
 import (
+	"encoding/json"
+
 	awssdkmodel "github.com/aws/aws-sdk-go/private/model/api"
 
-	"github.com/aws-controllers-k8s/code-generator/pkg/util"
+	"github.com/aws-controllers-k8s/code-generator/pkg/util"	
 )
 
+// StringArray is a type that can be represented in JSON as *either* a string
+// *or* an array of strings
+type StringArray []string
+
 // OperationConfig represents instructions to the ACK code generator to
 // specify the overriding values for API operation parameters and its custom implementation.
 type OperationConfig struct {
@@ -37,7 +43,8 @@ type OperationConfig struct {
 	ResourceName string `json:"resource_name"`
 	// Override for operation type in case of heuristic failure
 	// An example of this is `Put...` or `Register...` API operations not being correctly classified as `Create` op type
-	OperationType string `json:"operation_type"`
+	// OperationType []string `json:"operation_type"`
+	OperationType StringArray `json:"operation_type"`
 	// PrimaryIdentifierFieldName provides the name of the field that should be
 	// interpreted as the "primary" identifier field. This field will be used as
 	// the primary field for resource adoption.
@@ -75,3 +82,21 @@ func (c *Config) ListOpMatchFieldNames(
 	}
 	return rConfig.ListOperation.MatchFields
 }
+
+// UnmarshalJSON parses input for a either a string or
+// or a list and returns a StringArray.
+func (a *StringArray) UnmarshalJSON(b []byte) error {
+	var multi []string
+	err := json.Unmarshal(b, &multi)
+	if err != nil {
+		var single string
+		err := json.Unmarshal(b, &single)
+		if err != nil {
+			return err
+		}
+		*a = []string{single}
+	} else {
+		*a = multi
+	}
+	return nil
+}

pkg/model/sdk_helper.go

@@ -27,6 +27,7 @@ import (
 	ackgenconfig "github.com/aws-controllers-k8s/code-generator/pkg/generate/config"
 	"github.com/aws-controllers-k8s/code-generator/pkg/names"
 	"github.com/aws-controllers-k8s/code-generator/pkg/util"
+
 	awssdkmodel "github.com/aws/aws-sdk-go/private/model/api"
 )
 
@@ -206,11 +207,13 @@ func (a *SDKAPI) GetOperationMap(cfg *ackgenconfig.Config) *OperationMap {
 	// create an index of Operations by operation types and resource name
 	opMap := OperationMap{}
 	for opID, op := range a.API.Operations {
-		opType, resName := getOpTypeAndResourceName(opID, cfg)
-		if _, found := opMap[opType]; !found {
-			opMap[opType] = map[string]*awssdkmodel.Operation{}
+		opTypeArray, resName := getOpTypeAndResourceName(opID, cfg)
+		for _, opType := range opTypeArray {
+			if _, found := opMap[opType]; !found {
+				opMap[opType] = map[string]*awssdkmodel.Operation{}
+			}
+			opMap[opType][resName] = op
 		}
-		opMap[opType][resName] = op
 	}
 	a.opMap = &opMap
 	return &opMap
@@ -382,20 +385,22 @@ func (a *SDKAPI) SDKAPIInterfaceTypeName() string {
 }
 
 // Override the operation type and/or resource name if specified in config
-func getOpTypeAndResourceName(opID string, cfg *ackgenconfig.Config) (OpType, string) {
+func getOpTypeAndResourceName(opID string, cfg *ackgenconfig.Config) ([]OpType, string) {
 	opType, resName := GetOpTypeAndResourceNameFromOpID(opID)
+	opTypes := []OpType{opType}
 
-	if cfg != nil {
-		if operationConfig, exists := cfg.Operations[opID]; exists {
-			if operationConfig.OperationType != "" {
-				opType = OpTypeFromString(operationConfig.OperationType)
-			}
+	if cfg == nil {
+		return opTypes, resName
+	}
+	if operationConfig, exists := cfg.Operations[opID]; exists {
+		if operationConfig.ResourceName != "" {
+			resName = operationConfig.ResourceName
+		}
 
-			if operationConfig.ResourceName != "" {
-				resName = operationConfig.ResourceName
-			}
+		for _, operationType := range operationConfig.OperationType {
+			opType = OpTypeFromString(operationType)
+			opTypes = append(opTypes, opType)
 		}
 	}
-
-	return opType, resName
+	return opTypes, resName
 }