[Rule Request] Unused DynamoDB AttributeDefinitions

[PatMyron]

Declaring DynamoDB AttributeDefinitions without using them as keys led to errors like these:

Property AttributeDefinitions is inconsistent with the KeySchema of the table and the secondary indexes - CloudFormation

An error occurred (ValidationException) when calling the CreateTable operation: One or more parameter values were invalid: Some AttributeDefinitions are not used. AttributeDefinitions: [Album, Artist, Sales], keys used: [Album, Artist] - Boto

$ aws dynamodb create-table --table-name table --billing-mode PAY_PER_REQUEST --attribute-definitions AttributeName=Artist,AttributeType=S --key-schema AttributeName=Artist,KeyType=HASH AttributeName=SongTitle,KeyType=RANGE

An error occurred (ValidationException) when calling the CreateTable operation: Invalid KeySchema: Some index key attribute have no definition

$ aws dynamodb create-table --table-name table --billing-mode PAY_PER_REQUEST --attribute-definitions AttributeName=Artist,AttributeType=S AttributeName=SongTitle,AttributeType=S --key-schema AttributeName=Artist,KeyType=HASH

An error occurred (ValidationException) when calling the CreateTable operation: One or more parameter values were invalid: Number of attributes in KeySchema does not exactly match number of attributes defined in AttributeDefinitions

Minimal examples of templates that pass cfn-lint but fail to deploy: #1044

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https://stackoverflow.com/questions/38142870/cloudformation-insists-my-dynamodb-creation-json-is-invalid-but-i-cant-see-h
https://stackoverflow.com/questions/41915749/propertydefinition-inconsistent