Fix CockroachDB errors (#980)

* Fix CockroachDB error

```
at or near "default": syntax error (PQ::PQError)
  from lib/pg/src/pq/connection.cr:214:7 in 'handle_error'
  from lib/pg/src/pq/connection.cr:197:7 in 'handle_async_frames'
  from lib/pg/src/pq/connection.cr:173:7 in 'read'
  from lib/pg/src/pq/connection.cr:168:7 in 'read'
  from lib/pg/src/pq/connection.cr:446:31 in 'expect_frame'
  from lib/pg/src/pq/connection.cr:445:5 in 'expect_frame'
  from lib/pg/src/pg/statement.cr:18:5 in 'perform_query'
  from lib/pg/src/pg/statement.cr:35:14 in 'perform_exec'
  from lib/db/src/db/statement.cr:85:9 in 'perform_exec_and_release'
  from lib/db/src/db/statement.cr:70:7 in 'exec:args'
  from lib/db/src/db/query_methods.cr:275:7 in 'exec'
  from lib/avram/src/avram/migrator/runner.cr:60:7 in 'create_db'
  from lib/avram/src/avram/tasks/db/create.cr:20:5 in 'run_task'
  from lib/avram/src/avram/tasks/db/base_task.cr:6:7 in 'call'
  from spec/setup/database.cr:2:3 in '__crystal_main'
  from /home/runner/work/_temp/crystal-1.6.0-true-undefined/share/crystal/src/crystal/main.cr:115:5 in 'main_user_code'
```

* Improve CockroachDB compatibility

See <cockroachdb/cockroach#38931>.

* Add `restart_identity` parameter to `#truncate`

src/avram/database.cr

@@ -260,11 +260,15 @@ abstract class Avram::Database
         .map(&.table_name)
     end
 
-    def truncate
+    def truncate(*, cascade : Bool = true, restart_identity : Bool = true)
       return if table_names.empty?
 
-      statement = ("TRUNCATE TABLE #{table_names.map { |name| name }.join(", ")} RESTART IDENTITY CASCADE;")
-      database.exec statement
+      cascade_sql = cascade ? " CASCADE" : ""
+      restart_id_sql = restart_identity ? " RESTART IDENTITY" : ""
+      table_names_sql = table_names.join(", ")
+      sql = "TRUNCATE TABLE #{table_names_sql}#{restart_id_sql}#{cascade_sql}"
+
+      database.exec(sql)
     end
 
     def delete

src/avram/migrator/runner.cr

@@ -57,7 +57,7 @@ class Avram::Migrator::Runner
 
   def self.create_db(quiet? : Bool = false)
     DB.connect("#{credentials.connection_string}/#{db_user}") do |db|
-      db.exec "CREATE DATABASE #{db_name} WITH OWNER DEFAULT"
+      db.exec "CREATE DATABASE #{db_name}"
     end
     unless quiet?
       puts "Done creating #{db_name.colorize(:green)}"

src/avram/queryable.cr

@@ -53,10 +53,13 @@ module Avram::Queryable(T)
     #
     # To delete all data referenced by foreign keys as well, set *cascade*
     # to true.
-    def self.truncate(*, cascade : Bool = false)
+    def self.truncate(*, cascade : Bool = false, restart_identity : Bool = false)
       query = self.new
-      cascade_str = cascade ? " CASCADE" : ""
-      query.database.exec "TRUNCATE TABLE #{query.table_name}#{cascade_str}"
+      cascade_sql = cascade ? " CASCADE" : ""
+      restart_id_sql = restart_identity ? " RESTART IDENTITY" : ""
+      sql = "TRUNCATE TABLE #{query.table_name}#{restart_id_sql}#{cascade_sql}"
+
+      query.database.exec(sql)
     end
   end