Remove the release notes length limit (loic-sharma#687)

Kudos to @dncnkrs for the original implementation. 

This allows BaGet to index packages with large release notes, like https://www.nuget.org/packages/chocolatey/0.10.6.1

Author: loic-sharma

src/BaGet.Core/Entities/AbstractContext.cs

@@ -68,8 +68,7 @@ private void BuildPackageEntity(EntityTypeBuilder<Package> package)
                 .HasMaxLength(MaxPackageVersionLength);
 
             package.Property(p => p.ReleaseNotes)
-                .HasColumnName("ReleaseNotes")
-                .HasMaxLength(DefaultMaxStringLength);
+                .HasColumnName("ReleaseNotes");
 
             package.Property(p => p.Authors)
                 .HasMaxLength(DefaultMaxStringLength)

src/BaGet.Database.MySql/Migrations/20210919191554_RemoveReleaseNotesMaxLength.Designer.cs

@@ -0,0 +1,35 @@
+using System;
+using Microsoft.EntityFrameworkCore.Metadata;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+namespace BaGet.Database.MySql.Migrations
+{
+    public partial class RemoveReleaseNotesMaxLength : Migration
+    {
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AlterColumn<DateTime>(
+                name: "RowVersion",
+                table: "Packages",
+                rowVersion: true,
+                nullable: true,
+                oldClrType: typeof(DateTime),
+                oldType: "timestamp(6)",
+                oldNullable: true)
+                .Annotation("MySql:ValueGenerationStrategy", MySqlValueGenerationStrategy.ComputedColumn);
+        }
+
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AlterColumn<DateTime>(
+                name: "RowVersion",
+                table: "Packages",
+                type: "timestamp(6)",
+                nullable: true,
+                oldClrType: typeof(DateTime),
+                oldRowVersion: true,
+                oldNullable: true)
+                .OldAnnotation("MySql:ValueGenerationStrategy", MySqlValueGenerationStrategy.ComputedColumn);
+        }
+    }
+}

src/BaGet.Database.MySql/Migrations/20210919191554_RemoveReleaseNotesMaxLength.cs

@@ -14,7 +14,7 @@ protected override void BuildModel(ModelBuilder modelBuilder)
         {
 #pragma warning disable 612, 618
             modelBuilder
-                .HasAnnotation("ProductVersion", "3.1.1")
+                .HasAnnotation("ProductVersion", "3.1.18")
                 .HasAnnotation("Relational:MaxIdentifierLength", 64);
 
             modelBuilder.Entity("BaGet.Core.Package", b =>
@@ -87,8 +87,7 @@ protected override void BuildModel(ModelBuilder modelBuilder)
 
                     b.Property<string>("ReleaseNotes")
                         .HasColumnName("ReleaseNotes")
-                        .HasColumnType("longtext CHARACTER SET utf8mb4")
-                        .HasMaxLength(4000);
+                        .HasColumnType("longtext CHARACTER SET utf8mb4");
 
                     b.Property<string>("RepositoryType")
                         .HasColumnType("varchar(100) CHARACTER SET utf8mb4")