Add option to encode value keys with '.' separators

[gKits]

Description

The Encoder struct has now a method called ActivateKeySeparation.
When this option is activated the keys of the values map[string][]string
will be the full path containing all names of the nested struct fields separated
by a period (.).

This also fixes the bug referenced in #228 that it is currently not possible to
decode values into structs with nested fields after encoding said structs.

I'm not sure about the naming so I'm open for suggestions if someone has better ideas.

Example

f := Foo{
    X: "hello",
    Y: Bar{
        A: "world",
        B: true,
    },
}

vals := map[string][]string{}
encoder := schema.NewEncoder()
encoder.ActivateKeySeparation()

encoder.Encode(f, vals)
fmt.Println(vals) // output: map[y.a:[test] y.b:[true] x:[test]]

What type of PR is this? (check all applicable)

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update
• Go Version Update
• Dependency Update

Description

Related Tickets & Documents

• Related Issue [BUG] Encoding of nested struct is missing named prefix #228
• Closes [BUG] Encoding of nested struct is missing named prefix #228

Added/updated tests?

• Yes
• No, and this is why: please replace this line with details on why tests
  have not been included
• I need help with writing tests

Run verifications and test

• make verify is passing
• make test is passing

[gKits]

Make verify seems to fail due to some linter problems due to integer overflow conversions

[zak905]

Looks good overall. If I may be a bit picky, I believe we could find a name which is semantically better for the option. I am thinking about something like: keepKeyOriginalPath or just keyOrignalPath

Also, I believe the Activate word is not necessary at the beginning of the setter function name. To keep in line with other options you can use the name directly with a boolean argument. the ZeroEmpty option is an example: https://github.com/gorilla/schema/blob/main/decoder.go#L46

[gKits]

@zak905 Thanks for the feedback. I have changed the name of the option to KeyOriginalPath definitely sounds better than before.

[zak905]

LGTM, thanks for addressing the remark.

Waiting on @jaitaiwan feedback.