Fixes X-Registry-Auth encoding from base64 to url_safe base64

[apozsuse]

Issue

For authentication for push/pull operations over registries, the value the X-Registry-Auth HTTP header is the base64 encoded of the json dump of the authorization data.
Plain base64 encoding causes problems if + character is present in the base64 encoded value, as + is a special separator in HTTP headers. The request is rejected by registries if '+' is present in that base64 encoded data.

Fix

It's required to change the plain base64 encoding for url_safe base64 encoding, as this encoding avoid using the problematic characters for HTTP and that's the encoding the registries are expecting.

The base64 url_safe encoding is present already in podman client or docker or docker-py.

Tests

According to my tests, + appears in base64 encoded when punctuation characters are encoded, for example:

{
    "username": "'I(Bx}yr}~Dk",
    "password": "dycioxoqngpm",
    "email": "izcmhquyprda@domain.com",
    "serveraddress": "exwandvyvhqy"
}

Gets base64 encoded, showing the issue, as:

eyJ1c2VybmFtZSI6ICInSShCeH15cn1+RGsiLCAicGFzc3dvcmQiOiAiZHljaW94b3FuZ3BtIiwgImVtYWlsIjogIml6Y21ocXV5cHJkYUBkb21haW4uY29tIiwgInNlcnZlcmFkZHJlc3MiOiAiZXh3YW5kdnl2aHF5In0=

[openshift-ci]

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This pull-request has been approved by: apozsuse
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[apozsuse]

Closing the PR to fix the issue with the commit.