* Make IoT certificate id generation deterministic
Fixes#3321
As per https://stackoverflow.com/questions/55847788/how-does-aws-iot-generate-a-certificate-id,
the IoT certificate ID is the SHA256 fingerprint of the
certificate. Since moto doesn't generate full certificates we will
instead use the SHA256 hash of the passed certificate pem.
* Don't allow duplicate IoT certificates to be created
Fixes#3320
When using boto3, trying to register a certificate that already
exists will throw a ResourceAlreadyExistsException. Moto should
follow the same pattern to allow testing error handling code in
this area.
* append appropriate urls when scaffolding
* make dispatch for rest-api
* fix dispatch for rest-json
* fix moto/core/response to obtain path and body parameters
* small fixes
* remove unused import
* fix get_int_param
* Add features of things and thing-types
* fix scaffold
* basic crud of cert
* support basic CRUD of policy
* refactor
* fix formatting of scaffold
* support principal_pocicy
* support thing_principal
* update readme
* escape service to handle service w/ hyphen like iot-data
* escape service w/ hyphen
* fix regexp to extract region from url
* escape service
* Implement basic iota-data feature
* iot-data shadow delta
* update readme
* remove unused import
* remove comment
* fix syntax
* specify region when creating boto3 client for test
* use uuid for seed of generating cert id
* specify region_name to iotdata client in test
* specify region to boto3 client in moto response
* excude iot and iotdata tests on server mode
* fix handling of thingTypeName in describe-thing
* test if server is up for iot
