customize timestamps options and indexes

[geminigeek]

hi,

currently timestamps creates createdAt and updatedAt and make index on same, i am proposing an option objects where we can pick and choose what keys are created and on which index is made.

use case large amount of logs or delayed logs , where updatedAt is irrelevant and the actual time stamp on the data is important (sensor data timestamp)

timestamps : true  // creates both key and index current behavior

timestamps :{
createdAt:true, // create  Key and index
updatedAt:false, // Key not created
}

timestamps :{
createdAt:true,
updatedAt:{index:false}, // create key not index
}