Support From and To static factory methods

[TimothyMakkison]

Is your feature request related to a problem? Please describe.
Many objects provide static methods instead of constructors for semantic reasons. Unfortunately as Mapperly is unable to use them users have to manually provide wrapper methods. Based upon.

Solution

Mapperly should look for static methods that meet the following criteria:

• static methods on the target type named From{SourceType.Name} accepting the source type as a single parameter and the target type as return type
• static methods on the source type named To{TargetType.Name} accepting the source type as single parameter returning the target type

Implementation

• This should be used as a fallback for if there are no compatible constructors. Should look for the target types From methods before looking for the source To methods.
• Perhaps the sources To methods could include non static methods.

var target = new global::Mapperly_gRPC.HelloReply();
target.Message = response.Message;
target.ResponseTime = Timestamp.FromDateTimeOffset(response.ResponseTime);
return target;

See #1107.

[latonz]

I'm not sure to what you are referring by if there are no compatible constructors (are you referring to the ones used by CtorMappingBuilder or by NewInstanceObjectMemberMappingBuilder). IMO this new mappings should try to be built directly after CtorMappingBuilder.

IMO the following signatures could be supported (all ordinary, non-async methods returning TTarget):

TSource.ToTTarget()
static TTarget.Create(TSource)
static TTarget.FromTSource(TSource)
static TSource.ToTTarget(TSource)

I'd split them across two MappingBuilders: ConvertInstanceMethodMappingBuilder and ConvertStaticMethodMappingBuilder.

Hints for a contribution despite the contributing documentation:

• Create new entries in Riok.Mapperly.Abstractions.MappingConversionType
• Create new *MappingBuilders, Riok.Mapperly.Descriptors.MappingBuilders.ParseMappingBuilder can be used as an idea how it could work
• Register the new TryBuildMapping methods in Riok.Mapperly.Descriptors.MappingBuilders.MappingBuilder._builders