fix: updated merge functionality

[james-milligan]

Signed-off-by: James-Milligan [email protected]

This PR

• flag updates are handled on a per source basis, allowing deletions to be recognised
• adds the Source method to the sync provider interface, returning a string

Related Issues

Fixes #181

How to test

make build
./flagd start -f config/samples/example_flags.json --sync-provider filepath

curl -X POST "localhost:8013/schema.v1.Service/ResolveInt" -d '{"flagKey":"myIntFlag","context":{"color":"yellow"}}' -H "Content-Type: application/json"

returns

{"value":"1", "reason":"DEFAULT", "variant":"one"}

Now change the name of the myIntFlag in config/samples/example_flags.json to notMyIntFlag

curl -X POST "localhost:8013/schema.v1.Service/ResolveInt" -d '{"flagKey":"myIntFlag","context":{"color":"yellow"}}' -H "Content-Type: application/json"

returns

{"code":"not_found","message":"FlagdError:, FLAG_NOT_FOUND"}

[beeme1mr]

Ran it locally and it worked great.