Making the path of conjur.properties configurable

[bnasslahsen]

Desired Outcome

• The goal of this PR is to make the path of conjur.properties configurable through spring-boot properties
• The current is hardcoding the path of the conjur.properties, making it possible to declare the path of secrets after the binary (jars, docker images, ...) are built.

Implemented Changes

Describe how the desired outcome above has been achieved with this PR. In
particular, consider:

This PR introduces new property conjur.mapping-path that allow the developer to explicitly set the path of conjur.properties

Definition of Done

At least 1 todo must be completed in the sections below for the PR to be
merged.

Changelog

• The CHANGELOG has been updated, or
• This PR does not include user-facing changes and doesn't require a
  CHANGELOG update

Test coverage

• This PR includes new unit and integration tests to go with the code
  changes, or
• The changes in this PR do not require tests

Documentation

• Docs (e.g. READMEs) were updated in this PR
• A follow-up issue to update official docs has been filed here: [insert issue ID]
• This PR does not require updating any documentation

Behavior

• This PR changes product behavior and has been reviewed by a PO, or
• These changes are part of a larger initiative that will be reviewed later, or
• No behavior was changed with this PR

Security

• Security architect has reviewed the changes in this PR,
• These changes are part of a larger initiative with a separate security review, or
• There are no security aspects to these changes

[stefanskicyber]

Code looks ok.
Changes were tested.