Mid parental height

[a-wei-william]

added for mid_parental_height:

• endpoint
• schema for request
• shcema for response

I'm not sure what to call the endpoint function because the imported function from global_function is already named mid_parental_height

[a-wei-william]

its failing the test_openapi_spec test

[eatyourpeas]

Thanks for this - this is good work: I have updated your function (and schemas) to return an SDS and centile for the midparental height also. These additions ended up in another branch inadvertently so I will close this and merge that.