Fix lora alpha and metadata handling

[tanuj-rai]

What does this PR do?

This PR adds --lora_alpha and metadata handling in training scripts in 'train_dreambooth_lora_sdxl.py'.

Part of #11730

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• [X] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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Who can review?

@linoytsaban @sayakpaul

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[tanuj-rai]

thanks! made some small changes

Thank you @linoytsaban , for reviewing and suggesting changes. I’ve implemented the requested updates.

[linoytsaban]

thanks @Tanuj-rai :) I just noticed lora_alpha is missing from the text_encoder config, after that's merged we'd be good to go https://github.com/huggingface/diffusers/blob/4f69b28e5521a1d5b62dce97668a046f45a9e32e/examples/dreambooth/train_dreambooth_lora_sdxl.py#L1245-L1249

[tanuj-rai]

thanks @Tanuj-rai :) I just noticed lora_alpha is missing from the text_encoder config, after that's merged we'd be good to go

https://github.com/huggingface/diffusers/blob/4f69b28e5521a1d5b62dce97668a046f45a9e32e/examples/dreambooth/train_dreambooth_lora_sdxl.py#L1245-L1249

Thank you @linoytsaban for pointing it out. I have now added the lora_alpha in the text_encoder config.

[sayakpaul]

@bot /style

[linoytsaban]

@sayakpaul yep, but I can take care of it in a separate PR, wdyt?

[sayakpaul]

Okay for me.

[linoytsaban]

@bot /style