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This PR adds support to handle the custom jinja function
`raise_exception` and passes the `bos` and `eos` tokens into the
template

Additionally this PR adds 3 tests to validate and show examples of what
can and cannot be parsed currently.

```bash
cargo test --package text-generation-router --lib -- infer::tests --nocapture
#     Finished test [unoptimized + debuginfo] target(s) in 7.82s
#      Running unittests src/lib.rs (target/debug/deps/text_generation_router-18a0bbf99c2ca1b4)

# running 3 tests
# test infer::tests::test_chat_template_valid_with_raise ... ok
# test infer::tests::test_chat_template ... ok
# test infer::tests::test_chat_template_invalid_with_raise ... ok

# test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 15 filtered out; finished in 0.00s
```