[Step 1] Allow constraint validation for path, query and header parameters

[TharmiganK]

Description:

Implementing the first step of Add constraint support for path, query and header params #3239

This task is to implement automatic constraint validations for path, query and header parameters if the parameter type is defined with constraints.

Describe your task(s)

The following use cases should be verified:

• Path parameter type

  @constraint:Int { minValue: 1, maxValue: 100 }
  type Id int;
  
  resource function get users/[Id id]() returns User {
      ...
  }

• Rest path parameter type

  @constraint:String { pattern: re`[a-zA-Z]+` }
  type Path string;
  
  resource function get [Path ...path]() returns http:Response {
      ...
  }

• Query parameter basic type

  @constraint:String { minLength: 2, maxLength: 20 }
  type UserName string;
  
  resource function get users(UserName name) returns user {
      ...
  }

• Query parameter basic type optional

  @constraint:String { minLength: 2, maxLength: 20 }
  type UserName string;
  
  resource function get users(UserName? name) returns User {
      ...
  }

• Query parameter basic type default negative

  @constraint:String { minLength: 2, maxLength: 20 }
  type UserName string;
  
  resource function get users(UserName name = "a") returns User {
      ...
  }

• Query parameter basic array type

  @constraint:String { minLength: 2, maxLength: 20 }
  type UserName string;
  
  @constraint:Array { minLength: 1, maxLength: 5}
  type UserNames UserName[];
  
  resource function get users(UserNames names) returns User[] {
      ...
  }

• Query parameter map type

  @constraint:Int { minValue: 18, maxValue: 100}
  type Age int;
  
  type UserDetails record {|
      @constraint:String { minLength: 2, maxLength: 20 }
      string name;
      Age age;
  |};
  
  resource function get users(UserDetails details) returns User {
      ...
  }

• Header parameter basic type

  @constraint:String { minLength: 2, maxLength: 20 }
  type UserName string;
  
  resource function get users(@http:Header UserName x\-name) returns User {
      ...
  }

• Header parameter basic type optional

  @constraint:String { minLength: 2, maxLength: 20 }
  type UserName string;
  
  resource function get users(@http:Header UserName? x\-name) returns User {
      ...
  }

• Header parameter basic type default negative

  @constraint:String { minLength: 2, maxLength: 20 }
  type UserName string;
  
  resource function get users(@http:Header UserName x\-name = "a") returns User {
      ...
  }

• Header parameter basic array type

  @constraint:String { minLength: 2, maxLength: 20 }
  type UserName string;
  
  @constraint:Array { minLength: 1, maxLength: 5}
  type UserNames UserName[];
  
  resource function get users(@http:Header UserNames x\-names) returns User[] {
      ...
  }

• Header parameter map type

  @constraint:Int { minValue: 18, maxValue: 100}
  type Age int;
  
  type UserDetails record {|
      @constraint:String { minLength: 2, maxLength: 20 }
      string x\-name?;
      @constraint:Array { maxLength : 2 }
      Age[] x\-ages?;
  |};
  
  resource function get users(@http:Header UserDetails details) returns User|User[] {
      ...
  }

[TharmiganK]

With the above PR, all the constraint validation errors (including path parameter) are returned as 400 - Bad Request responses. Initially, it was planned to give a 404 - Not Found response for constraint validation failure in the path parameter but later we have decided to give the same response to be consistent. Will think about this later