741 custom character stat storing

[Iir0R]

Brief description

Updated customCharacter.service to meet required changes in #741 Custom character stat storing. Also changes to tests.

Change list

• New function: addValues, gets document as POJO, adds matching base stats, returns result.
• New function: getFieldsToUpdate, adds key value pairs to correct key, $inc or $set.
• createOne creates a new character with stat deltas starting at 0, returns base + deltas.
• readOneById, readOne, readMany and readPlayerBattleCharacters use addValues, return base + deltas.
• updateOneById and updateOneByCondition use getFieldsToUpdate to increment deltas and set others.
• Changes to tests custom character files to match new results.

[hoan301298]

Sorry for this inconvenience, but this PR has many changes and need to be tested later on. I am still reviewing it. Thanks