Update wording, memoize states

Update docs

app/graphql/resolvers/concerns/issue_resolver_fields.rb

@@ -15,10 +15,10 @@ module IssueResolverFields
               description: 'Labels applied to this issue'
     argument :milestone_title, GraphQL::STRING_TYPE.to_list_type,
               required: false,
-              description: 'Milestones applied to this issue'
+              description: 'Milestone applied to this issue'
     argument :assignee_username, GraphQL::STRING_TYPE,
               required: false,
-              description: 'Username of a user assigned to the issues'
+              description: 'Username of a user assigned to the issue'
     argument :assignee_id, GraphQL::STRING_TYPE,
               required: false,
               description: 'ID of a user assigned to the issues, "none" and "any" values supported'
@@ -56,7 +56,7 @@ module IssueResolverFields
     parent = object.respond_to?(:sync) ? object.sync : object
     return Issue.none if parent.nil?
 
-    # Will need to be be made group & namespace aware with
+    # Will need to be made group & namespace aware with
     # https://gitlab.com/gitlab-org/gitlab-foss/issues/54520
     args[:iids] ||= [args.delete(:iid)].compact if args[:iid]
     args[:attempt_project_search_optimizations] = true if args[:search].present?

app/graphql/types/issue_status_counts_type.rb

@@ -7,8 +7,12 @@ module Types
 
     authorize :read_issue
 
+    def self.available_issue_states
+      @available_issue_states ||= Issue.available_states.keys.push('all')
+    end
+
     ::Gitlab::IssuablesCountForState::STATES.each do |state|
-      next unless Issue.available_states.keys.push('all').include?(state)
+      next unless available_issue_states.include?(state.downcase)
 
       field state,
             GraphQL::INT_TYPE,

doc/api/graphql/reference/gitlab_schema.graphql

@@ -5606,7 +5606,7 @@ type Group {
     assigneeId: String
 
     """
-    Username of a user assigned to the issues
+    Username of a user assigned to the issue
     """
     assigneeUsername: String
 
@@ -5666,7 +5666,7 @@ type Group {
     last: Int
 
     """
-    Milestones applied to this issue
+    Milestone applied to this issue
     """
     milestoneTitle: [String]
 
@@ -10213,7 +10213,7 @@ type Project {
     assigneeId: String
 
     """
-    Username of a user assigned to the issues
+    Username of a user assigned to the issue
     """
     assigneeUsername: String
 
@@ -10258,7 +10258,7 @@ type Project {
     labelName: [String]
 
     """
-    Milestones applied to this issue
+    Milestone applied to this issue
     """
     milestoneTitle: [String]
 
@@ -10303,7 +10303,7 @@ type Project {
     assigneeId: String
 
     """
-    Username of a user assigned to the issues
+    Username of a user assigned to the issue
     """
     assigneeUsername: String
 
@@ -10343,7 +10343,7 @@ type Project {
     labelName: [String]
 
     """
-    Milestones applied to this issue
+    Milestone applied to this issue
     """
     milestoneTitle: [String]
 
@@ -10383,7 +10383,7 @@ type Project {
     assigneeId: String
 
     """
-    Username of a user assigned to the issues
+    Username of a user assigned to the issue
     """
     assigneeUsername: String
 
@@ -10443,7 +10443,7 @@ type Project {
     last: Int
 
     """
-    Milestones applied to this issue
+    Milestone applied to this issue
     """
     milestoneTitle: [String]
 

doc/api/graphql/reference/gitlab_schema.json

@@ -15615,7 +15615,7 @@
                 },
                 {
                   "name": "milestoneTitle",
-                  "description": "Milestones applied to this issue",
+                  "description": "Milestone applied to this issue",
                   "type": {
                     "kind": "LIST",
                     "name": null,
@@ -15629,7 +15629,7 @@
                 },
                 {
                   "name": "assigneeUsername",
-                  "description": "Username of a user assigned to the issues",
+                  "description": "Username of a user assigned to the issue",
                   "type": {
                     "kind": "SCALAR",
                     "name": "String",
@@ -30531,7 +30531,7 @@
                 },
                 {
                   "name": "milestoneTitle",
-                  "description": "Milestones applied to this issue",
+                  "description": "Milestone applied to this issue",
                   "type": {
                     "kind": "LIST",
                     "name": null,
@@ -30545,7 +30545,7 @@
                 },
                 {
                   "name": "assigneeUsername",
-                  "description": "Username of a user assigned to the issues",
+                  "description": "Username of a user assigned to the issue",
                   "type": {
                     "kind": "SCALAR",
                     "name": "String",
@@ -30742,7 +30742,7 @@
                 },
                 {
                   "name": "milestoneTitle",
-                  "description": "Milestones applied to this issue",
+                  "description": "Milestone applied to this issue",
                   "type": {
                     "kind": "LIST",
                     "name": null,
@@ -30756,7 +30756,7 @@
                 },
                 {
                   "name": "assigneeUsername",
-                  "description": "Username of a user assigned to the issues",
+                  "description": "Username of a user assigned to the issue",
                   "type": {
                     "kind": "SCALAR",
                     "name": "String",
@@ -30919,7 +30919,7 @@
                 },
                 {
                   "name": "milestoneTitle",
-                  "description": "Milestones applied to this issue",
+                  "description": "Milestone applied to this issue",
                   "type": {
                     "kind": "LIST",
                     "name": null,
@@ -30933,7 +30933,7 @@
                 },
                 {
                   "name": "assigneeUsername",
-                  "description": "Username of a user assigned to the issues",
+                  "description": "Username of a user assigned to the issue",
                   "type": {
                     "kind": "SCALAR",
                     "name": "String",