Document how CRSAuthorityFactory dynamically compose at run time

It is easy do get lost with the numerous indirection levels with AuthorityFactory in the referencing module. A document that explains what happens on the first call to CRS.decode(xxx) down to the SPI level would be very helpful. Some of the main classes involved are:

<table class='confluenceTable'><tbody>
<tr>
<th class='confluenceTh'> Class </th>
<th class='confluenceTh'> purpose </th>
</tr>
<tr>
<td class='confluenceTd'> FactoryUsingSQL </td>
<td class='confluenceTd'> for reading the EPSG database </td>
</tr>
<tr>
<td class='confluenceTd'> BufferedAuthorityFactory </td>
<td class='confluenceTd'> for caching </td>
</tr>
<tr>
<td class='confluenceTd'> OrderedAxisAuthorityFactory </td>
<td class='confluenceTd'> for changing axis order to (x,y) </td>
</tr>
<tr>
<td class='confluenceTd'> FallbackAuthorityFactory </td>
<td class='confluenceTd'> for chaining standard EPSG codes with user's extensions </td>
</tr>
<tr>
<td class='confluenceTd'> AllAuthorityFactories </td>
<td class='confluenceTd'> for querying all authority namespaces (EPSG, AUTO2...) </td>
</tr>
</tbody></table>

Legend for the attached screenshot:
<table class='confluenceTable'><tbody>
<tr>
<th class='confluenceTh'> Label </th>
<th class='confluenceTh'> meaning </th>
</tr>
<tr>
<td class='confluenceTd'> crs </td>
<td class='confluenceTd'> Provides CRS services, either as CRSFactory or CRSAuthorityFactory. </td>
</tr>
<tr>
<td class='confluenceTd'> cs </td>
<td class='confluenceTd'> Provides CS services, either as CSFactory or CSAuthorityFactory. </td>
</tr>
<tr>
<td class='confluenceTd'> datum </td>
<td class='confluenceTd'> Provides datum services, either as DatumFactory or DatumAuthorityFactory. </td>
</tr>
<tr>
<td class='confluenceTd'> operation </td>
<td class='confluenceTd'> Provides coordinate operation services. </td>
</tr>
<tr>
<td class='confluenceTd'> buffered </td>
<td class='confluenceTd'> Caches any object previously created. </td>
</tr>
<tr>
<td class='confluenceTd'> optional </td>
<td class='confluenceTd'> Implements the OptionalFactory interface. </td>
</tr>
<tr>
<td class='confluenceTd'> registered </td>
<td class='confluenceTd'> Service discovered from some META-INF/services/ directory. </td>
</tr>
</tbody></table>