Survey contacts generation for model selection

This module links two existing features: generating contacts from survey answers and survey questions whose answer is a record chosen from a model. It is installed automatically when both features are present.

What changes for users:

• On a survey question of the model-selection type, the list of contact fields you can map the answer to is now limited to fields on the contact that point to exactly the same model as the question, accept one or many records, are stored and are not read-only.
• If you try to map the answer to a contact field that points to a different model, Odoo blocks the configuration with a clear error message naming the field, the question and the two models involved.
• When a contact is created from the survey answers, the selected record(s) are written into the mapped contact field: a single record for a one-to-one field, or the full set of selected records for a many-to-many field.

It touches the survey question configuration (survey.question) and the survey answer processing (survey.user_input). No new menus or screens are added; the behaviour appears inside the existing survey configuration and contact-generation flow.