Add scala-pekko client generator

[mickaelmagniez]

pekko is a fork of akka, which has recently change its licence to Business Source License.

Now than pekko-http 1.0.0 is released, openapi-generator can support pekko-http for client generation.

I've done a new generator rather than adding a flag to the scala-akka generator, because i've updated all dependencies, and removed joda-time and compat libraries

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@clasnake @jimschubert @shijinkui @ramzimaalej @chameleon82 @Bouillie @Fish86

[wing328]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

[wing328]

tested locally and the result is good

[info] Fetched artifacts of 
[info] compiling 15 Scala sources to /Users/williamcheng/Code/openapi-generator7/samples/client/petstore/scala-pekko/target/scala-2.13/classes ...
[warn] /Users/williamcheng/Code/openapi-generator7/samples/client/petstore/scala-pekko/src/main/scala/org/openapitools/client/api/EnumsSerializers.scala:24:64: Wrap `enum` in backticks to use it as an identifier, it will become a keyword in Scala 3. [quickfixable]
[warn]   private class EnumNameSerializer[E <: Enumeration: ClassTag](enum: E)
[warn]                                                                ^
[warn] one warning found
[success] Total time: 34 s, completed 21 Dec. 2023, 7:42:38 pm

[mickaelmagniez]

Thanks for the review, i've updated the commit author, and added the scala-pekko sample to ci

[wing328]

lgtm. thanks for the contribution.

I'l file a follow-up PR with minor enhancement.

happy holidays!