[API] Get comment stats in date range

[bodynar]

Use #10, after #12

Add API for gathering comment appearance count change in specific data range.
Represent data as pairs of values:

• key: date \ interval value
• value: appearance count for specific date

API should get 3 values:

• Start date
• End date (must be greater than start date)
• Interval type (day \ week \ month \ year)
  Third parameter should be used for grouping count.

Restrictions for intervals: Do not perform execution if difference between dates is:

• Day - More than 30 days
• Week - More than 30 weeks
• Month - More than 30 month

---

Example:

• 01-01-2020
• 30-01-2020
• Week
  API should return:

[
    { "commentId": [
        { "date": 01-01-2020, "value": 10 }, // Appearance count = 10 on 01-01-2020
        { "date": 08-01-2020, "value": 11 }, // Appearance count = 11 on 08-01-2020
        { "date": 15-01-2020, "value": 21 }, // Appearance count = 21 on 15-01-2020
        { "date": 22-01-2020, "value": 25 }, // Appearance count = 25 on 22-01-2020
        { "date": 29-01-2020, "value": 26 }, // Appearance count = 26 on 29-01-2020
        { "date": 30-01-2020, "value": 26 }, // Appearance count = 26 on 30-01-2020
     ] },
     // ...
]

If end date is not captured in last full interval (like week, but it's 1 day, like in example above) - it should be added as another value with end date