[EXTERNAL] Fixes Amazon subscription period parsing (#1813) by @tessm…

…erandre (#1828)

### Checklist
- [x] If applicable, unit tests
- [x] If applicable, create follow-up issues for `purchases-ios` and
hybrids

### Motivation
<!-- Why is this change required? What problem does it solve? --> Amazon
subscription periods were being incorrectly parsed.


https://developer.amazon.com/docs/in-app-purchasing/iap-implement-iap.html#successful-request

<!-- Please link to issues following this format: Resolves #999999 -->
Resolves #1771

### Description
Amazon returns annual and semiannual subscription periods as `Annual`
and `SemiAnnual`. Please look at the

[docs](https://developer.amazon.com/docs/in-app-purchasing/iap-implement-iap.html#successful-request)
for more information.

Contributed by @tessmerandre

---------

Co-authored-by: André Tessmer <tessmerandre@gmail.com>

purchases/src/main/kotlin/com/revenuecat/purchases/amazon/storeProductConversions.kt

@@ -47,8 +47,12 @@ internal fun String.createPeriod(): Period? {
         "Monthly" -> Period(1, Period.Unit.MONTH, "P1M")
         "BiMonthly" -> Period(2, Period.Unit.MONTH, "P2M")
         "Quarterly" -> Period(3, Period.Unit.MONTH, "P3M")
-        "SemiAnnually" -> Period(6, Period.Unit.MONTH, "P6M")
-        "Annually" -> Period(1, Period.Unit.YEAR, "P1Y")
+        "SemiAnnually",
+        "SemiAnnual",
+        -> Period(6, Period.Unit.MONTH, "P6M")
+        "Annually",
+        "Annual",
+        -> Period(1, Period.Unit.YEAR, "P1Y")
 
         // Handle "7 Days" or "14 Days" or "1 Month" just in case
         else -> this.split(" ")

purchases/src/test/java/com/revenuecat/purchases/amazon/ProductConverterTest.kt

@@ -154,7 +154,9 @@ class PeriodParsingTest(private val periodRaw: String, private val periodExpecte
                 arrayOf("BiMonthly", Period(2, Period.Unit.MONTH, "P2M")),
                 arrayOf("Quarterly", Period(3, Period.Unit.MONTH, "P3M")),
                 arrayOf("SemiAnnually", Period(6, Period.Unit.MONTH, "P6M")),
+                arrayOf("SemiAnnual", Period(6, Period.Unit.MONTH, "P6M")),
                 arrayOf("Annually", Period(1, Period.Unit.YEAR, "P1Y")),
+                arrayOf("Annual", Period(1, Period.Unit.YEAR, "P1Y")),
                 arrayOf("7 Days", Period(7, Period.Unit.DAY, "P7D")),
                 arrayOf("14 Weeks", Period(14, Period.Unit.WEEK, "P14W")),
                 arrayOf("1 Year", Period(1, Period.Unit.YEAR, "P1Y")),