Add PatternReplaceTokenFilter Flags property (#4086)

Closes #4085

Author: Andrew Welburn

src/Nest/Analysis/CharFilters/PatternReplaceCharFilter.cs

@@ -7,6 +7,9 @@ namespace Nest
 	/// </summary>
 	public interface IPatternReplaceCharFilter : ICharFilter
 	{
+		[DataMember(Name ="flags")]
+		string Flags { get; set; }
+
 		[DataMember(Name ="pattern")]
 		string Pattern { get; set; }
 
@@ -19,6 +22,9 @@ public class PatternReplaceCharFilter : CharFilterBase, IPatternReplaceCharFilte
 	{
 		public PatternReplaceCharFilter() : base("pattern_replace") { }
 
+		/// <inheritdoc />
+		public string Flags { get; set; }
+
 		/// <inheritdoc />
 		public string Pattern { get; set; }
 
@@ -31,9 +37,15 @@ public class PatternReplaceCharFilterDescriptor
 		: CharFilterDescriptorBase<PatternReplaceCharFilterDescriptor, IPatternReplaceCharFilter>, IPatternReplaceCharFilter
 	{
 		protected override string Type => "pattern_replace";
+
+		string IPatternReplaceCharFilter.Flags { get; set; }
 		string IPatternReplaceCharFilter.Pattern { get; set; }
 		string IPatternReplaceCharFilter.Replacement { get; set; }
 
+		/// <inheritdoc />
+		public PatternReplaceCharFilterDescriptor Flags(string flags) =>
+			Assign(flags, (a, v) => a.Flags = v);
+
 		/// <inheritdoc />
 		public PatternReplaceCharFilterDescriptor Pattern(string pattern) =>
 			Assign(pattern, (a, v) => a.Pattern = v);

src/Tests/Tests/Analysis/CharFilters/CharFilterTests.cs

@@ -17,9 +17,9 @@ public class MappingTests : CharFilterAssertionBase<MappingTests>
 
 		public class PatternReplaceTests : CharFilterAssertionBase<PatternReplaceTests>
 		{
-			public override FuncTokenizer Fluent => (n, cf) => cf.PatternReplace(n, c => c.Pattern("x").Replacement("y"));
-			public override ICharFilter Initializer => new PatternReplaceCharFilter { Pattern = "x", Replacement = "y" };
-			public override object Json => new { pattern = "x", replacement = "y", type = "pattern_replace" };
+			public override FuncTokenizer Fluent => (n, cf) => cf.PatternReplace(n, c => c.Flags("CASE_INSENSITIVE").Pattern("x").Replacement("y"));
+			public override ICharFilter Initializer => new PatternReplaceCharFilter { Flags = "CASE_INSENSITIVE", Pattern = "x", Replacement = "y" };
+			public override object Json => new { flags = "CASE_INSENSITIVE", pattern = "x", replacement = "y", type = "pattern_replace" };
 			public override string Name => "pr";
 		}