[MM-57517] Add exact user ID lookup to the search query for Users (#26661)

* [MM-57517] Add exact user ID lookup to the search query for Users

* Fix lint

* Add test for ID search

server/channels/store/sqlstore/user_store.go

@@ -1613,6 +1613,8 @@ func generateSearchQuery(query sq.SelectBuilder, terms []string, fields []string
 			}
 			termArgs = append(termArgs, fmt.Sprintf("%%%s%%", strings.TrimLeft(term, "@")))
 		}
+		searchFields = append(searchFields, "Id = ?")
+		termArgs = append(termArgs, strings.TrimLeft(term, "@"))
 		query = query.Where(fmt.Sprintf("(%s)", strings.Join(searchFields, " OR ")), termArgs...)
 	}
 

server/channels/store/storetest/user_store.go

@@ -2862,6 +2862,30 @@ func testUserStoreSearch(t *testing.T, rctx request.CTX, ss store.Store) {
 			},
 			[]*model.User{u3},
 		},
+		{
+			"search for Id of u1",
+			t1id,
+			u1.Id,
+			&model.UserSearchOptions{
+				AllowFullNames: true,
+				Limit:          model.UserSearchDefaultLimit,
+				Roles:          []string{},
+				TeamRoles:      []string{},
+			},
+			[]*model.User{u1},
+		},
+		{
+			"search for partial Id of u1",
+			t1id,
+			u1.Id[:len(u1.Id)-1],
+			&model.UserSearchOptions{
+				AllowFullNames: true,
+				Limit:          model.UserSearchDefaultLimit,
+				Roles:          []string{},
+				TeamRoles:      []string{},
+			},
+			[]*model.User{},
+		},
 	}
 
 	for _, testCase := range testCases {