Add Replace interface to cater for Certificate instances.

Install interface is implemented by Manager class and
Certificate class for different purposes, so seperated
the interfaces.

Install interface will be implemented by Manager class
to create an instance of Certificate object and install
the certificate after validation

Replace interface will be implemented by Certificate class
to replace existing certificate.

A certificate has certificate and private key portion, user
is allowed to replace certificate portion.

NotAllowed error added to Install interface, to limit the
number of certificates installed.

Moved InvalidCertificate error to base level so that it
can be used by Replace and Install interfaces.

Install.error.yaml and Install.metadata.yaml errors are used
by phosphor-certificate-manager. Need to remove these files
after certificate manager uses Certs.error.yaml

Change-Id: I6a1196fa69284b694e67726fad26bd9c37232c70
Signed-off-by: Marri Devender Rao <devenrao@in.ibm.com>
diff --git a/xyz/openbmc_project/Certs/Install.interface.yaml b/xyz/openbmc_project/Certs/Install.interface.yaml
index 8781834..5fe9c1d 100644
--- a/xyz/openbmc_project/Certs/Install.interface.yaml
+++ b/xyz/openbmc_project/Certs/Install.interface.yaml
@@ -4,6 +4,7 @@
     - name: Install
       description: >
           Install the certificate and restart the associated services.
+          NotAllowed error thrown if certificate already exists.
       parameters:
         - name: Path
           type: string
@@ -13,4 +14,5 @@
               certificate and private key).
       errors:
         - xyz.openbmc_project.Common.Error.InternalFailure
-        - xyz.openbmc_project.Certs.Install.Error.InvalidCertificate
+        - xyz.openbmc_project.Common.Error.NotAllowed
+        - xyz.openbmc_project.Certs.Error.InvalidCertificate