refactor: Implement use of Pagination DTO

[GHkrishna]

About

• We have implemented pagination DTO [libs/common/src/dtos/pagination.dto.ts]
• This DTO is used to sort and get the required data as per the need
• It is used in Get endpoints

Current behavior

• There are some instances [apps/api-gateway/src/connection/dtos/get-all-connections.dto.ts] where pagination is separately implemented.
• Here's an example

export class GetAllConnectionsDto {
  @ApiProperty({ required: false, example: '1' })
  @Transform(({ value }) => toNumber(value))
  @IsOptional()
  pageNumber: number = 1;

  @ApiProperty({ required: false, example: '10' })
  @IsOptional()
  @Transform(({ value }) => toNumber(value))
  @Min(1, { message: 'Page size must be greater than 0' })
  @Max(100, { message: 'Page size must be less than 100' })
  pageSize: number = 10;

  @ApiProperty({ required: false })
  @IsOptional()
  @Transform(({ value }) => trim(value))
  @Type(() => String)
  searchByText: string = '';

  @ApiProperty({
    required: false
  })
  @Transform(({ value }) => trim(value))
  @IsOptional()
  @IsEnum(SortFields)
  sortField: string = SortFields.CREATED_DATE_TIME;

  @ApiProperty({
    enum: [SortValue.DESC, SortValue.ASC],
    required: false
  })
  @Transform(({ value }) => trim(value))
  @IsOptional()
  @IsEnum(SortValue)
  sortBy: string = SortValue.DESC;
} 

Expected behavior

Instead a better way would be to extend and make use of the already existing PaginationDto.
So the above implementation would become something like:

export class GetAllConnectionsDto extends PaginationDto {
  @ApiProperty({
    required: false
  })
  @Transform(({ value }) => trim(value))
  @IsOptional()
  @IsEnum(SortFields)
  sortField: string = SortFields.CREATED_DATE_TIME;

  @ApiProperty({
    enum: [SortValue.DESC, SortValue.ASC],
    required: false
  })
  @Transform(({ value }) => trim(value))
  @IsOptional()
  @IsEnum(SortValue)
  sortBy: string = SortValue.DESC;
} 

Note

• The changes made on DTO level (in variable names, if any) in API-gateway should also be reflected all the way to the individual service where the actual parameters will be used for a db call or elsewhere.
• Eg.: For the above DTO [GetAllConnectionsDto], the changes made for function [async getConnections] in [apps/api-gateway/src/connection/connection.controller.ts] would change the variable 'searchByText' to 'search'.
• Hence the changes would be in following files:
  • [apps/api-gateway/src/connection/connection.controller.ts] and respective Dto 'GetAllConnectionsDto' in [apps/api-gateway/src/connection/dtos/get-all-connections.dto.ts]
  • [apps/api-gateway/src/connection/connection.service.ts] ans the respective interface 'IConnectionSearchCriteria' in [apps/api-gateway/src/interfaces/IConnectionSearch.interface.ts]
  • [apps/connection/src/connection.controller.ts] and the respective interface 'IFetchConnections' in [apps/connection/src/interfaces/connection.interfaces.ts]
  • [apps/connection/src/connection.service.ts] and the respective interface 'IConnectionSearchCriteria' in [apps/connection/src/interfaces/connection.interfaces.ts]