General infinity literals for DateTimeOffset min/max values (#2390)

Fixes #2389

Author: roji

src/EFCore.PG/Storage/Internal/Mapping/NpgsqlTimestampTzTypeMapping.cs

@@ -58,6 +58,19 @@ private string GenerateLiteralCore(object value)
                 };
 
             case DateTimeOffset dateTimeOffset:
+                if (!NpgsqlTypeMappingSource.DisableDateTimeInfinityConversions)
+                {
+                    if (dateTimeOffset == DateTimeOffset.MinValue)
+                    {
+                        return "-infinity";
+                    }
+
+                    if (dateTimeOffset == DateTimeOffset.MaxValue)
+                    {
+                        return "infinity";
+                    }
+                }
+
                 return dateTimeOffset.ToString("yyyy-MM-dd HH:mm:ss.FFFFFFzzz", CultureInfo.InvariantCulture);
 
             default:

test/EFCore.PG.Tests/Storage/NpgsqlTypeMappingTest.cs

@@ -125,6 +125,14 @@ public void GenerateSqlLiteral_returns_timestamptz_infinity_literals()
         Assert.Equal(
             "TIMESTAMPTZ 'infinity'",
             GetMapping("timestamptz").GenerateSqlLiteral(DateTime.MaxValue));
+
+        Assert.Equal(
+            "TIMESTAMPTZ '-infinity'",
+            GetMapping("timestamptz").GenerateSqlLiteral(DateTimeOffset.MinValue));
+
+        Assert.Equal(
+            "TIMESTAMPTZ 'infinity'",
+            GetMapping("timestamptz").GenerateSqlLiteral(DateTimeOffset.MaxValue));
     }
 
     [Fact]