Support answering stage questions and bulk article customizations

[amamd07]

Extends ReviewCustomizations (rayyan/reviews/customizations.py) to cover both shapes of the /customize endpoint.

• customize() gains optional scope and allow_string_value, so a customization can target a specific question's answer_key.
• answer_question(id, article_id, stage_id, question_id, answer, key="included", allow_string_value=True) — encodes a single value or list into the plan shape the API expects. The question's answer_key (scope) is built inside the SDK from stage_id/question_id via stage_question_answer_key() / STAGE_QUESTION_ANSWER_KEY_TEMPLATE, so callers never assemble the key format themselves.
• bulk_customizations() now accepts article_ids as a list/tuple or comma-separated string and normalizes to the comma-separated string the endpoint requires.
• set_label() and set_reason() — add/remove a label or exclusion reason. Both delegate to a shared _set_customization helper: value=1 (add) uses the bulk params form in one request; value=-1 (remove) uses the per-article plan form, applied to each article. This sets the given key rather than toggling — other customizations already on an article are left unchanged. The __EXR__ reason prefix and the remove value live in named constants (EXCLUSION_REASON_PREFIX, REMOVE_VALUE).
• Package version bumped 1.0rc16 → 1.0rc17 (setup.cfg).

No breaking changes — all new parameters are optional and existing signatures are preserved. Note: set_label/set_reason return a single response when adding and a list of per-article responses when removing.

[maboelnour]

If an article already has a customization and this method is called to add a new one, the existing customization won't be toggled.

[amamd07]

That's correct, I had the decision customization in mind. I've renamed it to _set_customization and updated the docstring to note it sets the key rather than toggling.

[maboelnour]

Should this form be in a constant?

[amamd07]

It was only for clarification. But your comment got me thinking that the construction belongs to the sdk. I moved the construction here and created a template and helper that constructs it. Thanks!