[POC] Basic server type serde for RestJson1 (#737)

* Initial implementation of RestJson and Http ser/de

Signed-off-by: Bigo <1781140+crisidev@users.noreply.github.com>

* Visitor render operation shapes from server generators

Signed-off-by: Bigo <1781140+crisidev@users.noreply.github.com>

* Use a symlink for the ebs test model

* Revert "Use a symlink for the ebs test model"

This reverts commit 0c2adcbf12f452959252134b7fbb9c70dab154c7.

* Now the model is emitted in different files

* A little more general model generation

Signed-off-by: Bigo <1781140+crisidev@users.noreply.github.com>

* Use a very simple model to try the service generators

* Move serializer in its own folder

* Initial implementation of RestJson and Http ser/de

Signed-off-by: Bigo <1781140+crisidev@users.noreply.github.com>

* Visitor render operation shapes from server generators

Signed-off-by: Bigo <1781140+crisidev@users.noreply.github.com>

* Use a symlink for the ebs test model

* Revert "Use a symlink for the ebs test model"

This reverts commit 0c2adcbf12f452959252134b7fbb9c70dab154c7.

* Now the model is emitted in different files

* A little more general model generation

Signed-off-by: Bigo <1781140+crisidev@users.noreply.github.com>

* Use a very simple model to try the service generators

* Move serializer in its own folder

* Refactor RestJson to accomodate upstream changes

* Refactor a little RestJson1 and add simple RFC doc

* Remove inheritance from Json ser/de and refactor codegen visitor to
directly use the rendering functions

* Make operation.rs module public

* Use the protocol ID instead of its string representation

Signed-off-by: Bigo <1781140+crisidev@users.noreply.github.com>