Skip settings migration if the settings value has not been changed

[unnawut]

Issue/Task Number: #798
Closes #798

Overview

This PR skips migration of a specific settings if the settings value has not been changed.
This helps remove unnecessary database writes and activity logs caused by unchanged settings updates.

Changes

• Updated EWallet.ReleaseTasks.ConfigMigration to skip updating if a settings value is unchanged.

Implementation Details

The Settings and StoredSettings is pretty complicated and adds a lot of changes to the changeset. Since this settings migration command mainly takes ENV values and saves to database, this PR skips unnecessary DB updates by checking whether the settings value changed. Only if it changed then it proceeds with the update.

Usage

Running this command the first time:

BASE_URL=http://localhost mix omg.config -m -y

Would result in:

Migrating the settings to the database...
  - Setting `base_url` to "http://localhost"... Done.

However, running it with the same value again would result in:

Migrating the settings to the database...
  - Setting `base_url` is already "http://localhost"... Skipping.

Impact

No changes to API specs or DB schemas.