Added PostgreSQL schema generator (BETA) (#20255)

* Initial version of PostgreSQL schema generator 'postgresql-schema' (based on 'mysql-schema' generator code)

* PostgreSQL schema generator. Initial version.

* Tested. Fixed errors. Documentation updated.

* Samples for 'postgresql-schema' updated.

* Removed current date/time from mustache templates for postgresql-schema generator.
Re-created samples.

* Re-created docs file for postgresql-schema generator.

* Removed unecessary LocalTime computing code and imports for postgresql-schema generator.

* Errors fixed for postgresql-schema generator. Samples recreated.

* Docs updated.

README.md

@@ -1139,6 +1139,7 @@ Here is a list of template creators:
    * GraphQL: @wing328 [:heart:](https://www.patreon.com/wing328)
    * Ktorm: @Luiz-Monad
    * MySQL: [@ybelenko](https://github.com/ybelenko)
+   * PostgreSQL: [@iri](https://github.com/iri)
    * Postman Collection: @gcatanese
    * Protocol Buffer: @wing328
    * WSDL: @adessoDpd

bin/configs/postgresql-schema-petstore.yaml

@@ -0,0 +1,5 @@
+generatorName: postgresql-schema
+outputDir: samples/schema/petstore/postgresql
+inputSpec: modules/openapi-generator/src/test/resources/3_0/petstore.yaml
+templateDir: modules/openapi-generator/src/main/resources/postgresql-schema
+

docs/generators.md

@@ -168,6 +168,7 @@ The following generators are available:
 * [graphql-schema](generators/graphql-schema.md)  
 * [ktorm-schema (beta)](generators/ktorm-schema.md)  
 * [mysql-schema](generators/mysql-schema.md)  
+* [postgresql-schema (beta)](generators/postgresql-schema.md)  
 * [postman-collection (beta)](generators/postman-collection.md)  
 * [protobuf-schema (beta)](generators/protobuf-schema.md)  
 * [wsdl-schema (beta)](generators/wsdl-schema.md)