* Refactor TLS parsing
The ParsePEMBundle and ParsePKIJSON functions in the certutil package assumes
both a client certificate and a custom CA are specified. Cassandra needs to
allow for either a client certificate, a custom CA, or both. This revamps the
parsing of pem_json and pem_bundle to accomodate for any of these configurations
1) In backends, ensure they are now using TokenPolicies
2) Don't reassign auth.Policies until after expmgr registration as we
don't need them at that point
Fixes#4829
* redoing connection handling
* a little more cleanup
* empty implementation of rotation
* updating rotate signature
* signature update
* updating interfaces again :(
* changing back to interface
* adding templated url support and rotation for postgres
* adding correct username
* return updates
* updating statements to be a list
* adding error sanitizing middleware
* fixing log sanitizier
* adding postgres rotate test
* removing conf from rotate
* adding rotate command
* adding mysql rotate
* finishing up the endpoint in the db backend for rotate
* no more structs, just store raw config
* fixing tests
* adding db instance lock
* adding support for statement list in cassandra
* wip redoing interface to support BC
* adding falllback for Initialize implementation
* adding backwards compat for statements
* fix tests
* fix more tests
* fixing up tests, switching to new fields in statements
* fixing more tests
* adding mssql and mysql
* wrapping all the things in middleware, implementing templating for mongodb
* wrapping all db servers with error santizer
* fixing test
* store the name with the db instance
* adding rotate to cassandra
* adding compatibility translation to both server and plugin
* reordering a few things
* store the name with the db instance
* reordering
* adding a few more tests
* switch secret values from slice to map
* addressing some feedback
* reinstate execute plugin after resetting connection
* set database connection to closed
* switching secret values func to map[string]interface for potential future uses
* addressing feedback
* Fix cassandra tests, explicitly set cluster port if provided
* Update cassandra.yml test-fixture
* Add port as part of the config option, fix tests
* Remove hostport splitting in cassandraConnectionProducer.createSession
* Include port in API docs
* WIP on mongodb plugin
* Add mongodb plugin
* Add tests
* Update mongodb.CreateUser() comment
* Update docs
* Add missing docs
* Fix mongodb docs
* Minor comment and test updates
* Fix imports
* Fix dockertest import
* Set c.Initialized at the end, check for empty CreationStmts first on CreateUser
* Remove Initialized check on Connection()
* Add back Initialized check
* Update docs
* Move connProducer and credsProducer into pkg for mongodb and cassandra
* Chage parseMongoURL to be a private func
* Default to admin if no db is provided in creation_statements
* Update comments and docs
Michael Golowka