[HackWeek] Generated builders understand default field values from IR

[cflems]

Before this PR

Context: https://github.com/palantir/conjure/pull/1615

After this PR

Hooks into the new IR definition including defaults in order to generate bean builders that understand these default values. Since these builders are used by Jackson to deserialize wire and storage types, this enables null or missing field values to be interpreted for backwards compatibility.

==COMMIT_MSG== Generated builders understand default field values from IR ==COMMIT_MSG==

[changelog-app[bot]]

Generate changelog in changelog-dir>`changelog/@unreleased`</changelog-dir

What do the change types mean?

- `feature`: A new feature of the service. - `improvement`: An incremental improvement in the functionality or operation of the service. - `fix`: Remedies the incorrect behaviour of a component of the service in a backwards-compatible way. - `break`: Has the potential to break consumers of this service's API, inclusive of both Palantir services and external consumers of the service's API (e.g. customer-written software or integrations). - `deprecation`: Advertises the intention to remove service functionality without any change to the operation of the service itself. - `manualTask`: Requires the possibility of manual intervention (running a script, eyeballing configuration, performing database surgery, ...) at the time of upgrade for it to succeed. - `migration`: A fully automatic upgrade migration task with no engineer input required. _Note: only one type should be chosen._

How are new versions calculated?

- ❗The `break` and `manual task` changelog types will result in a major release! - 🐛 The `fix` changelog type will result in a minor release in most cases, and a patch release version for patch branches. This behaviour is configurable in autorelease. - ✨ All others will result in a minor version release.

Type

- [ ] Feature - [ ] Improvement - [ ] Fix - [ ] Break - [ ] Deprecation - [ ] Manual task - [ ] Migration

Description

Generated builders understand default field values from IR **Check the box to generate changelog(s)** - [ ] Generate changelog entry

[cflems]

A couple things. One, this depends on the PR in conjure, so right now it's on a mavenLocal version and the checks are going to fail until the upstream is merged. Two, this presents an opportunity to do something very useful by way of separating wire-format deserializing builders from userland builders. This would allow deserialization to maintain backwards compatibility without presenting the same options to developers, forcing them to write code conforming to updated object formats and eliminating an entire class of bugs that comes along with insufficiently strict builders.