style(spdx): spotless apply correct SPDX license id

[sambacha]

This changes only the 'SPDX-License-Identifier' in selected contracts. Contracts either had no
License Header, in that case the entire line was added or the previous license was amended to
ssp-1.0. additionally, the main 'LICENSE' file was amended to reflect the changes. the only other
modification done to a non '*.sol' file was .gitignore in which '.DS_Store' was appended to the
bottom.

[milkyklim]

Doggie, I am fine changing the modifiers cause we already went away from "what is on chain" paradigm.

[sambacha]

will resolve the conflicting files

[fubuloubu]

Is this necessary? I usually ask for editor-specific files for people to put in their global git ignore

[sambacha]

It is in fact specific to mac os x. I added it as I thought this may sneak in, as I use a remote dev box and my laptop, I will remove it in the updated patch.

Brings up a great point, an official style guide and coding conventions would be great.

[fubuloubu]

I'm not a license person, but this is not a license I know enough about. Can we have a pros/cons list, and an explanation of why this is good for Yearn?

[sambacha]

https://gist.github.com/sambacha/bb914c3ff1041503e80a70651e62184f

[sambacha]

 
-13. Remote Network Interaction; Use with the GNU General Public License.
-Notwithstanding any other provision of this License, if you modify the Program, your modified version must prominently offer all users interacting with it remotely through a computer network (if your version supports such interaction) an opportunity to receive the Corresponding Source of your version by providing access to the Corresponding Source from a network server at no charge, through some standard or customary means of facilitating copying of software. This Corresponding Source shall include the Corresponding Source for any work covered by version 3 of the GNU General Public License that is incorporated pursuant to the following paragraph.
+13. Offering the Program as a Service.
+If you make the functionality of the Program or a modified version available to third parties as a service, you must make the Service Source Code available via network download to everyone at no charge, under the terms of this License. Making the functionality of the Program or modified version available to third parties as a service includes, without limitation, enabling third parties to interact with the functionality of the Program or modified version remotely through a computer network, offering a service the value of which entirely or primarily derives from the value of the Program or modified version, or offering a service that accomplishes for users the primary purpose of the Program or modified version.
 
-Notwithstanding any other provision of this License, you have permission to link or combine any covered work with a work licensed under version 3 of the GNU General Public License into a single combined work, and to convey the resulting work. The terms of this License will continue to apply to the part which is the covered work, but the work with which it is combined will remain governed by version 3 of the GNU General Public License.
+"Service Source Code" means the Corresponding Source for the Program or the modified version, and the Corresponding Source for all programs that you use to make the Program or modified version available as a service, including, without limitation, management software, user interfaces, application program interfaces, automation software, monitoring software, backup software, storage software and hosting software, all such that a user could run an instance of the service using the Service Source Code you make available.
 
 14. Revised Versions of this License.
-The Free Software Foundation may publish revised and/or new versions of the GNU Affero General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.
+MongoDB, Inc. may publish revised and/or new versions of the Server Side Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.
 
-Each version is given a distinguishing version number. If the Program specifies that a certain numbered version of the GNU Affero General Public License "or any later version" applies to it, you have the option of following the terms and conditions either of that numbered version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of the GNU Affero General Public License, you may choose any version ever published by the Free Software Foundation.
+Each version is given a distinguishing version number. If the Program specifies that a certain numbered version of the Server Side Public License "or any later version" applies to it, you have the option of following the terms and conditions either of that numbered version or of any later version published by MongoDB, Inc. If the Program does not specify a version number of the Server Side Public License, you may choose any version ever published by MongoDB, Inc.
 
-If the Program specifies that a proxy can decide which future versions of the GNU Affero General Public License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Program.
+If the Program specifies that a proxy can decide which future versions of the Server Side Public License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Program.

The terms of SSPL-1.0 are more for specific about how you may use the code in commercial activities.

Here is an example of where the ambiguities of free software licensing can cause some confusion: https://twitter.com/NateHindman/status/1289345690942885889
https://twitter.com/NoahZinsmeister/status/1289309266734538757

MongoDB Created this license after what happened with the use of MongoDB and a certain cloud service provider and their own version of the database.

[sambacha]

opening a new PR