ProtocolURI path component in DRLs MUST be base64url encoded

[LiranCohen]

Through testing apps and DRLs we've concluded that base64url encoding the protocol URI in the path segments is best.

We particularly ran into this issue with nginx https://trac.nginx.org/nginx/ticket/786 where nginx decides to decode then re-encode the path segment which removes one of the slashes from the protocol URI.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 80.32787% with 12 lines in your changes missing coverage. Please review.

Project coverage is 94.92%. Comparing base (295be4a) to head (5f9f2ff).

Files with missing lines	Patch %	Lines
src/http-api.ts	80.32%	12 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #168 +/- ## ========================================== + Coverage 94.89% 94.92% +0.03% ========================================== Files 28 28 Lines 2956 2976 +20 Branches 397 401 +4 ========================================== + Hits 2805 2825 +20 Misses 150 150 Partials 1 1 ```

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