Use Case

As an auto encryption user,
I want want my options to be unmodified,
So that I can reuse them without being worried about unexpected data.

Pretty easy to reproduce:

// freeze auto encryption options
const autoEncryption = Object.freeze({
    keyVaultNamespace,
    kmsProviders: getKmsProviders(),
    extraOptions
  });

const client = new MongoClient(.., { autoEncryption });

// throws:      TypeError: Cannot add property keyVaultClient, object is not extensible

User Experience

I don't think this has much of an actual impact - users are unlikely to re-use auto encryption options across multiple clients.  I noticed this when sharing auto encryption options across mocha tests, because after the first test finished and closed its client, the second test fails because the auto encryption options have been mutated and now contain a closed `keyVaultClient`.  This throws when we use it in the state machine because we cannot auto connect an explicitly closed client.

n/a

Risks/Unknowns

None

Acceptance Criteria

Implementation Requirements

• Prevent mutation of auto encryption options
  • We could deep copy them before using them, or store any properties we need to add to them somewhere else.

Testing Requirements

Documentation Requirements

None.

Follow Up Requirements

None.