endpoint supports create/update of sessions

Here is an example of possible fields that are extracted from the District System.

In the District System, ServiceDateID is the Key ID while in Salesforce, the Key ID should be a combination of Salesforce Team Season ID + Date. This assumes that there will only be max of one session per day.

```
{
"_id" : "district_1_87654321",
"ServiceDate" : "Tuesday, October 27, 2020",
"BeginTime" : "3:00 PM",
"EndTime" : "4:00 PM",
"ServiceDateID" : "87654321",
"district" : "district_1",
"ActivityType" : "Soccer Practice",
"ActivityName" : "School Name 2020-2021",
"ActivityCategory" : "Skill Building/Enrichment",
"ActivityDescription" : "Coaches will lead soccer practices",
"ActivitySite" : "Virtual Learning",
"ActivityID" : "1234567890"
}
```