(SP:5) Migration task: Update the old cooperations according to the current scheme

[PavloButynets]

1. Delete all cooperations that contain a non-existent initiator or receiver
2. In old cooperations where the proficiencyLevel field is of type [string], change the type to string:
   • if the array contains one element, then just convert it to string
   • if there are several, then take the average value
3. Delete fields:
   • category
   • subject
   • languages
4. Add fields:
   • title
   • section (type: [Object])
     • If the sections field is present, it must conform to the current structure:

     sections:[
     {
       title: { type: String, required: true },
       description: { type: String, required: true },
       resources: [
         {
           resource: { type: Schema.Types.ObjectId, required: true },
           resourceType: { type: String },
           availability: { status: { type: String }, date: { type: Date } },
           completionStatus: { type: String }
         }
       ]
      }
     ]
     

5. Rename the description field to additionalInfo

Testing
Write tests that check the correctness of migration:

1. Testing the removal of cooperations with non-existent initiator or receiver
2. Correct creation of title and section fields in documents where there is no such field
3. Checking the absence of category, subject languages ​​and description fields after migration
4. Checking the presence of additionalInfo fields in all documents
5. MOST IMPORTANT: A test that checks whether the migration changes only the incorrect documents and does not affect the correct or all documents