Prevent Nightscout collisions from occurring when a transmitter ID is recycled (#285)

* Update DexcomSourceG5.swift

Generate unique _id value to prevent Mongo collisions in Nightscout

* Update DexcomSourceG6.swift

Generate unique _id value to prevent Mongo collisions in Nightscout

FreeAPS/Sources/APS/CGM/DexcomSourceG5.swift

@@ -148,7 +148,7 @@ extension DexcomSourceG5: CGMManagerDelegate {
                 let quantity = newGlucoseSample.quantity
                 let value = Int(quantity.doubleValue(for: .milligramsPerDeciliter))
                 return BloodGlucose(
-                    _id: newGlucoseSample.syncIdentifier,
+                    _id: UUID().uuidString,
                     sgv: value,
                     direction: .init(trendType: newGlucoseSample.trend),
                     date: Decimal(Int(newGlucoseSample.date.timeIntervalSince1970 * 1000)),

FreeAPS/Sources/APS/CGM/DexcomSourceG6.swift

@@ -153,7 +153,7 @@ extension DexcomSourceG6: CGMManagerDelegate {
                     let quantity = newGlucoseSample.quantity
                     let value = Int(quantity.doubleValue(for: .milligramsPerDeciliter))
                     return BloodGlucose(
-                        _id: newGlucoseSample.syncIdentifier,
+                        _id: UUID().uuidString,
                         sgv: value,
                         direction: .init(trendType: newGlucoseSample.trend),
                         date: Decimal(Int(newGlucoseSample.date.timeIntervalSince1970 * 1000)),