Add missing types in yaml schema (#1600)

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### Pull Request Checklist:
- [x] This PR addresses an already opened issue (for bug fixes /
features)
    - This PR fixes #1595
- [ ] Tests for the changes have been added (for bug fixes / features)
- [x] (If applicable) Documentation has been added / updated (for bug
fixes / features)
- [x] CHANGES.rst has been updated (with summary of main changes)
- [x] Link to issue (:issue:`number`) and pull request (:pull:`number`)
has been added

### What kind of change does this PR introduce?

* Allows "str" for indicator parameter "src_freq"
* Allows "kind : int" for indicator parameter's parameters.

### Does this PR introduce a breaking change?
No, it simply validates yaml definition that were supported before.

### Other information:
I added a note to the module doc about "kind" and how it is meant to be
used in a yaml.

CHANGES.rst

@@ -15,7 +15,7 @@ Announcements
 New features and enhancements
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 * Added uncertainty partitioning method `lafferty_sriver` from Lafferty and Sriver (2023), which can partition uncertainty related to the downscaling method. (:issue:`1497`, :pull:`1529`).
-* Validate YAML indicators description before trying to build module. (:issue:`1523`, :pull:`1560`).
+* Validate YAML indicators description before trying to build module. (:issue:`1523`, :issue:`1595`, :pull:`1560`, :pull:`1596`, :pull:`1600`).
 * Support ``indexer`` keyword in YAML indicator description. (:issue:`1522`, :pull:`1561`).
 * New ``xclim.core.calendar.stack_periods`` and ``unstack_periods`` for performing ``rolling(time=...).construct(..., stride=...)`` but with non-uniform temporal periods like years or months. They replace ``xclim.sdba.processing.construct_moving_yearly_window`` and ``unpack_moving_yearly_window`` which are deprecated and will be removed in a future release.
 

xclim/core/indicator.py

@@ -78,6 +78,8 @@
             units: <param units>  # Only valid if "compute" points to a generic function
             default : <param default>
             description: <param description>
+            kind: <param kind> # Override the parameter kind.
+                             # This is mostly useful for transforming an optional variable into a required one by passing ``kind: 0``.
         ...
       ...  # and so on.
 

xclim/data/schema.yml

@@ -10,7 +10,7 @@ variables: map(include('variable'), key=regex(r'^[\w]+$'), required=False)
 indicator:
   abstract: str(required=False)
   allowed_periods: list(enum('A', 'Q', 'M', 'W'), required=False)
-  src_freq: list(str(), required=False)
+  src_freq: any(str(), list(str()), required=False)
   base: str(required=False)
   compute: str(required=False)
   input: map(str(), key=str(), required=False)
@@ -32,6 +32,7 @@ parameter:
   default: any(str(), num(), bool(), null(), include('indexer'), required=False)
   choices: list(str(), required=False)
   units: str(required=False)
+  kind: int(required=False)
 
 indexer:
   drop: bool(required=False)