create a specific var for custom template and update generators

[HugoMario]

No description provided.

[Grandolf49]

@HugoMario In what release is this solved? I tried using 3.0.18 and facing the following error.

Exception in thread "Thread-0" java.lang.RuntimeException: Could not generate model 'AccountingRuleData'
        at io.swagger.codegen.v3.DefaultGenerator.generateModels(DefaultGenerator.java:451)
        at io.swagger.codegen.v3.DefaultGenerator.generate(DefaultGenerator.java:779)
        at io.swagger.codegen.v3.cli.cmd.Generate.run(Generate.java:360)
        at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: java.io.FileNotFoundException: /fineract-provider/config/swagger/templates/model.mustache
        at com.github.jknack.handlebars.io.URLTemplateLoader.sourceAt(URLTemplateLoader.java:70)
        at com.github.jknack.handlebars.Handlebars.compile(Handlebars.java:438)
        at com.github.jknack.handlebars.Handlebars.compile(Handlebars.java:419)
        at io.swagger.codegen.v3.templates.HandlebarTemplateEngine.getHandlebars(HandlebarTemplateEngine.java:48)
        at io.swagger.codegen.v3.templates.HandlebarTemplateEngine.getRendered(HandlebarTemplateEngine.java:24)
        at io.swagger.codegen.v3.DefaultGenerator.processTemplateToFile(DefaultGenerator.java:795)
        at io.swagger.codegen.v3.DefaultGenerator.generateModels(DefaultGenerator.java:438)

In version 3.0.21 I am getting this error

[Thread-0] ERROR i.s.parser.SwaggerCompatConverter - failed to read resource listing
com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'openapi': was expecting (JSON String, Number, Array, Object or token 'null', 'true' or 'false')
 at [Source: (StringReader); line: 1, column: 8]
        at com.fasterxml.jackson.core.JsonParser._constructError(JsonParser.java:1840)
        at com.fasterxml.jackson.core.base.ParserMinimalBase._reportError(ParserMinimalBase.java:722)
        at com.fasterxml.jackson.core.json.ReaderBasedJsonParser._reportInvalidToken(ReaderBasedJsonParser.java:2867)
        at com.fasterxml.jackson.core.json.ReaderBasedJsonParser._handleOddValue(ReaderBasedJsonParser.java:1913)
        at com.fasterxml.jackson.core.json.ReaderBasedJsonParser.nextToken(ReaderBasedJsonParser.java:772)
        at com.fasterxml.jackson.databind.ObjectMapper._readTreeAndClose(ObjectMapper.java:4247)
        at com.fasterxml.jackson.databind.ObjectMapper.readTree(ObjectMapper.java:2720)
        at io.swagger.parser.SwaggerCompatConverter.readResourceListing(SwaggerCompatConverter.java:210)
        at io.swagger.parser.SwaggerCompatConverter.read(SwaggerCompatConverter.java:123)
        at io.swagger.parser.SwaggerCompatConverter.readWithInfo(SwaggerCompatConverter.java:94)
        at io.swagger.parser.SwaggerParser.readWithInfo(SwaggerParser.java:42)
        at io.swagger.v3.parser.converter.SwaggerConverter.readLocation(SwaggerConverter.java:89)
        at io.swagger.parser.OpenAPIParser.readLocation(OpenAPIParser.java:16)
        at io.swagger.codegen.v3.config.CodegenConfigurator.toClientOptInput(CodegenConfigurator.java:517)
        at io.swagger.codegen.v3.cli.cmd.Generate.run(Generate.java:376)
        at java.base/java.lang.Thread.run(Thread.java:834)
Exception in thread "Thread-0" java.lang.RuntimeException: missing OpenAPI input!
        at io.swagger.codegen.v3.DefaultGenerator.generate(DefaultGenerator.java:768)
        at io.swagger.codegen.v3.cli.cmd.Generate.run(Generate.java:378)
        at java.base/java.lang.Thread.run(Thread.java:834)

It says my OpenAPI File is invalid but 3.0.18 is able to build the library (when templateDir is not specified)

Any idea how to resolve this?