feature(finisher_api): add Exists method

[demoManito]

• [x] Do only one thing
• [x] Non breaking API changes
• [x] Tested

What did this pull request do?

User Case Description

[demoManito]

Hi, can I add this method? If so, is it reasonable to add it this way, or should it be placed in the driver? @jinzhu

[jinzhu]

Maybe we should place it in a helper package, keeping GORM itself clean and avoiding adding too much API directly.

[demoManito]

Maybe we should place it in a helper package, keeping GORM itself clean and avoiding adding too much API directly.

Do you mean the helper package under the go-gorm organization? @jinzhu

[jinzhu]

For now, we probably won’t maintain an additional helper package. It could be placed in a separate third-party library for the time being.

[demoManito]

For now, we probably won’t maintain an additional helper package. It could be placed in a separate third-party library for the time being.

ok