Major - P3 When featureCompatibilityVersion is 3.2, it should be an error to insert documents containing NumberDecimal values in legacy write mode.
Previous description:
Documents that contain NumberDecimal values can be inserted in legacy write mode. The same documents cannot be inserted when using write command mode.
var coll = db.foo;
coll.drop();
// The write fails when using write commands:
// "Attempt to use a decimal BSON type when support is not currently enabled."
assert.writeError(coll.insert({a: NumberDecimal(2.0)}));
assert.eq(coll.count(), 0);
// The write succeeds when using legacy writes.
db.getMongo().forceWriteMode('legacy');
coll.insert({a: NumberDecimal(2.0)});
// This assertion fails because there's a document present.
assert.eq(coll.count(), 0);