Adds changes for optional/required fields in Java code generation · amazon-ion/ion-cli@127723e

The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2, actions-rs/toolchain@v1, actions-rs/cargo@v1. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/

The following actions use a deprecated Node.js version and will be forced to run on node20: actions/checkout@v2, actions-rs/toolchain@v1, actions-rs/cargo@v1. For more info: https://github.blog/changelog/2024-03-07-github-actions-all-actions-will-run-on-node20-instead-of-node16-by-default/

The `set-output` command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

The `set-output` command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

The `set-output` command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

The `set-output` command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

Cargo Test: code-gen-projects/rust/code-gen-demo/target/debug/build/code-gen-demo-8fc79c94e446c543/out/ion_generated_code.rs#L1

unused import: `IonResult`

Cargo Test: code-gen-projects/rust/code-gen-demo/target/debug/build/code-gen-demo-8fc79c94e446c543/out/ion_generated_code.rs#L134

unused import: `nested_type_1::NestedType1`

Cargo Test: code-gen-projects/rust/code-gen-demo/target/debug/build/code-gen-demo-8fc79c94e446c543/out/ion_generated_code.rs#L9

field `source` is never read

Cargo Test: code-gen-projects/rust/code-gen-demo/target/debug/build/code-gen-demo-8fc79c94e446c543/out/ion_generated_code.rs#L11

field `description` is never read

Cargo Test: code-gen-projects/rust/code-gen-demo/target/debug/build/code-gen-demo-8fc79c94e446c543/out/ion_generated_code.rs#L44

associated items `new`, `c`, `a`, and `b` are never used

Cargo Test: code-gen-projects/rust/code-gen-demo/target/debug/build/code-gen-demo-8fc79c94e446c543/out/ion_generated_code.rs#L146

associated items `new`, `d`, and `e` are never used

Cargo Test: code-gen-projects/rust/code-gen-demo/target/debug/build/code-gen-demo-8fc79c94e446c543/out/ion_generated_code.rs#L267

associated items `new` and `value` are never used

Cargo Test: code-gen-projects/rust/code-gen-demo/target/debug/build/code-gen-demo-8fc79c94e446c543/out/ion_generated_code.rs#L308

associated items `new` and `value` are never used

Cargo Test: code-gen-projects/rust/code-gen-demo/target/debug/build/code-gen-demo-8fc79c94e446c543/out/ion_generated_code.rs#L375

associated items `new`, `b`, `c`, `d`, and `a` are never used

unused `Result` that must be used

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