Map the FRS Adult Disability Payment and Child Disability Payment codes (117, 118, 121, 122) #500

The UKDA data dictionary for FRS 2024-25 (study 9563, benefits_ukda_data_dictionary.rtf) labels four BENEFITS codes:

• 117 = ADP (Daily Living) Scotland only;
• 118 = ADP (Mobility) Scotland only;
• 121 = Child Disability Payment (Care) Scotland only;
• 122 = Child Disability Payment (Mobility) Scotland only.

frs.py BENEFIT_CODES maps none of them. In the Enhanced FRS 2024-25, every raw ADP daily-living recipient has pip_dl_category NONE and no disability flag. They therefore miss the PIP-linked rules: the legacy premiums, the Pension Credit severe disability addition, UC disability proxies and others. ADP mirrors PIP's components and rates, and CDP mirrors DLA for children.

Proposed fix:

• confirm the code frame from the DWP FRS 2024-25 benefits documentation (Table 1);
• decide, with evidence, whether to map ADP into the PIP inputs and CDP into the DLA inputs. Check whether the PIP and DLA calibration targets are GB or England and Wales only, so the mapping does not double count against DWP targets;
• add tests and measure the effect with real policyengine-uk runs.

Codes 69 and 70 appear in the 2024-25 data with no value label in any document. Do not guess their meaning.

Found while reviewing PolicyEngine/policyengine-uk#1946 and #494.

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