Allow "+" and "=" characters in values of SpecificAssetIds in order to support base64 encoded values

[richaashara]

Problem description
I don't want to expose SpecificAssetIds' values directly while creating Digital Twin. So, I want to use base64 encoded value as value in SpecificAssetIds

Solution Proposal
We can just edit the regrex for validation of value of specificAssetIds which will allow base64 encoded value.

Note
This issue resembles to an issue in tractus-X. issue link: eclipse-tractusx/sldt-digital-twin-registry#391

[BirgitBoss]

@richaashara Seems this issue is not relevant any longer? See discussion in eclipse-tractusx/sldt-digital-twin-registry#391

[richaashara]

@BirgitBoss ,
We can close this issue now.

[BirgitBoss]

Thanks